diff --git a/examples/src/main/java/Shell.java b/examples/src/main/java/Shell.java
index 2b227d097af..2c5bfda3167 100644
--- a/examples/src/main/java/Shell.java
+++ b/examples/src/main/java/Shell.java
@@ -15,6 +15,7 @@
 import org.mozilla.javascript.JavaScriptException;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.WrappedException;
 
 /**
@@ -49,12 +50,13 @@ public static void main(String args[]) {
             // Initialize the standard objects (Object, Function, etc.)
             // This must be done before scripts can be executed.
             Shell shell = new Shell();
-            cx.initStandardObjects(shell);
+            TopLevel topLevel = new TopLevel(shell);
+            cx.initStandardObjects(topLevel);
 
             // Define some global functions particular to the shell. Note
             // that these functions are not part of ECMA.
             String[] names = {"print", "quit", "version", "load", "help"};
-            shell.defineFunctionProperties(names, Shell.class, ScriptableObject.DONTENUM);
+            shell.defineFunctionProperties(topLevel, names, Shell.class, ScriptableObject.DONTENUM);
 
             args = processOptions(cx, args);
 
@@ -202,7 +204,7 @@ public static double version(Context cx, Scriptable thisObj, Object[] args, Func
      * @param funObj the function object of the invoked JavaScript function
      */
     public static void load(Context cx, Scriptable thisObj, Object[] args, Function funObj) {
-        Shell shell = (Shell) getTopLevelScope(thisObj);
+        Shell shell = (Shell) getTopLevelScope(thisObj).getGlobalThis();
         for (int i = 0; i < args.length; i++) {
             shell.processSource(cx, Context.toString(args[i]));
         }
diff --git a/it-android/src/main/java/org/mozilla/javascript/android/TestCase.java b/it-android/src/main/java/org/mozilla/javascript/android/TestCase.java
index 2596e5bcd86..c055c5689d3 100644
--- a/it-android/src/main/java/org/mozilla/javascript/android/TestCase.java
+++ b/it-android/src/main/java/org/mozilla/javascript/android/TestCase.java
@@ -13,7 +13,7 @@
 import org.mozilla.javascript.ContextFactory;
 import org.mozilla.javascript.ScriptRuntime;
 import org.mozilla.javascript.Scriptable;
-import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 
 /**
  * Utility class, that search for testcases in "assets/tests".
@@ -25,7 +25,7 @@
 public abstract class TestCase {
 
     protected final String name;
-    protected final Scriptable global;
+    protected final TopLevel global;
 
     private static final ContextFactory factory =
             new ContextFactory() {
@@ -47,7 +47,7 @@ protected Context makeContext() {
                 }
             };
 
-    public TestCase(String name, Scriptable global) {
+    public TestCase(String name, TopLevel global) {
         this.name = name;
         this.global = global;
     }
@@ -55,9 +55,7 @@ public TestCase(String name, Scriptable global) {
     public String run() {
         Context cx = factory.enterContext();
         try {
-            Scriptable scope = cx.newObject(global);
-            scope.setPrototype(global);
-            scope.setParentScope(null);
+            Scriptable scope = TopLevel.createIsolate(global);
             return ScriptRuntime.toString(runTest(cx, scope));
         } finally {
             Context.exit();
@@ -74,7 +72,7 @@ public String toString() {
     public static class AssetScript extends TestCase {
         protected final AssetManager assetManager;
 
-        public AssetScript(String name, Scriptable global, AssetManager assetManager) {
+        public AssetScript(String name, TopLevel global, AssetManager assetManager) {
             super(name, global);
             this.assetManager = assetManager;
         }
@@ -94,7 +92,7 @@ public static List<TestCase> getTestCases(android.content.Context context) throw
 
         AssetManager assetManager = context.getAssets();
         // define assert object
-        ScriptableObject global;
+        TopLevel global;
         Context cx = factory.enterContext();
         try (InputStream in = assetManager.open("assert.js");
                 Reader rdr = new InputStreamReader(in, StandardCharsets.UTF_8)) {
diff --git a/it-android/src/main/java/org/mozilla/javascript/android/TypeInfoFactoryTestCase.java b/it-android/src/main/java/org/mozilla/javascript/android/TypeInfoFactoryTestCase.java
index 2d52707ba77..97f87bc59f0 100644
--- a/it-android/src/main/java/org/mozilla/javascript/android/TypeInfoFactoryTestCase.java
+++ b/it-android/src/main/java/org/mozilla/javascript/android/TypeInfoFactoryTestCase.java
@@ -2,6 +2,7 @@
 
 import org.mozilla.javascript.Context;
 import org.mozilla.javascript.Scriptable;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.lc.type.TypeInfoFactory;
 import org.mozilla.javascript.lc.type.impl.factory.ClassValueCacheFactory;
 
@@ -9,7 +10,7 @@
  * @author ZZZank
  */
 public class TypeInfoFactoryTestCase extends TestCase {
-    public TypeInfoFactoryTestCase(String name, Scriptable global) {
+    public TypeInfoFactoryTestCase(String name, TopLevel global) {
         super(name, global);
     }
 
diff --git a/rhino-engine/src/main/java/org/mozilla/javascript/engine/Builtins.java b/rhino-engine/src/main/java/org/mozilla/javascript/engine/Builtins.java
index a98536564c4..6e2715ddffa 100644
--- a/rhino-engine/src/main/java/org/mozilla/javascript/engine/Builtins.java
+++ b/rhino-engine/src/main/java/org/mozilla/javascript/engine/Builtins.java
@@ -47,7 +47,7 @@ void register(Context cx, ScriptableObject scope, ScriptContext sc) {
 
     private static Object print(Context cx, Scriptable scope, Scriptable thisObj, Object[] args) {
         try {
-            Builtins self = getSelf(thisObj);
+            Builtins self = getSelf(scope);
             for (Object arg : args) {
                 self.stdout.write(ScriptRuntime.toString(arg));
             }
diff --git a/rhino-engine/src/main/java/org/mozilla/javascript/engine/RhinoScriptEngine.java b/rhino-engine/src/main/java/org/mozilla/javascript/engine/RhinoScriptEngine.java
index 02c5399220c..5c09b35d3cb 100644
--- a/rhino-engine/src/main/java/org/mozilla/javascript/engine/RhinoScriptEngine.java
+++ b/rhino-engine/src/main/java/org/mozilla/javascript/engine/RhinoScriptEngine.java
@@ -25,6 +25,7 @@
 import org.mozilla.javascript.Script;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 
 /**
  * This is the implementation of the standard ScriptEngine interface for Rhino.
@@ -76,7 +77,7 @@ public class RhinoScriptEngine extends AbstractScriptEngine implements Compilabl
 
     private final RhinoScriptEngineFactory factory;
     private final Builtins builtins;
-    private ScriptableObject topLevelScope = null;
+    private TopLevel topLevelScope = null;
 
     RhinoScriptEngine(RhinoScriptEngineFactory factory) {
         this.factory = factory;
@@ -94,18 +95,17 @@ private Scriptable initScope(Context cx, ScriptContext sc) throws ScriptExceptio
             builtins.register(cx, topLevelScope, sc);
         }
 
-        Scriptable engineScope = new BindingsObject(sc.getBindings(ScriptContext.ENGINE_SCOPE));
-        engineScope.setParentScope(null);
-        engineScope.setPrototype(topLevelScope);
-
         if (sc.getBindings(ScriptContext.GLOBAL_SCOPE) != null) {
-            Scriptable globalScope = new BindingsObject(sc.getBindings(ScriptContext.GLOBAL_SCOPE));
-            globalScope.setParentScope(null);
-            globalScope.setPrototype(topLevelScope);
-            engineScope.setPrototype(globalScope);
+            var globalScope =
+                    TopLevel.createIsolate(
+                            topLevelScope,
+                            new BindingsObject(sc.getBindings(ScriptContext.GLOBAL_SCOPE)));
+            return TopLevel.createIsolate(
+                    globalScope, new BindingsObject(sc.getBindings(ScriptContext.ENGINE_SCOPE)));
+        } else {
+            return TopLevel.createIsolate(
+                    topLevelScope, new BindingsObject(sc.getBindings(ScriptContext.ENGINE_SCOPE)));
         }
-
-        return engineScope;
     }
 
     @Override
diff --git a/rhino-tools/src/main/java/org/mozilla/javascript/tools/debugger/Main.java b/rhino-tools/src/main/java/org/mozilla/javascript/tools/debugger/Main.java
index 598cf659b31..867aaf64a83 100644
--- a/rhino-tools/src/main/java/org/mozilla/javascript/tools/debugger/Main.java
+++ b/rhino-tools/src/main/java/org/mozilla/javascript/tools/debugger/Main.java
@@ -16,6 +16,7 @@
 import org.mozilla.javascript.ContextFactory;
 import org.mozilla.javascript.Kit;
 import org.mozilla.javascript.Scriptable;
+import org.mozilla.javascript.ScriptableObject;
 import org.mozilla.javascript.commonjs.module.ModuleScope;
 import org.mozilla.javascript.tools.shell.Global;
 
@@ -180,7 +181,7 @@ public static void main(String[] args) {
             global.installRequire(cx, List.of(), false);
 
             URI uri = new File(System.getProperty("user.dir")).toURI();
-            ModuleScope scope = new ModuleScope(global, uri, null);
+            ScriptableObject scope = ModuleScope.createModuleScope(global, uri, null);
 
             main.setScope(scope);
 
diff --git a/rhino-tools/src/main/java/org/mozilla/javascript/tools/shell/Global.java b/rhino-tools/src/main/java/org/mozilla/javascript/tools/shell/Global.java
index 275eb0bb0c2..9998d1a9b2b 100644
--- a/rhino-tools/src/main/java/org/mozilla/javascript/tools/shell/Global.java
+++ b/rhino-tools/src/main/java/org/mozilla/javascript/tools/shell/Global.java
@@ -97,9 +97,12 @@ public class Global extends ImporterTopLevel {
     private static final String[] prompts = {"js> ", "  > "};
     private HashMap<String, String> doctestCanonicalizations;
 
-    public Global() {}
+    public Global() {
+        super(true);
+    }
 
     public Global(Context cx) {
+        super(true);
         init(cx);
     }
 
@@ -128,7 +131,7 @@ public void init(Context cx) {
         // that these functions are not part of ECMA.
         initStandardObjects(cx, sealedStdLib);
         NativeConsole.init(this, sealedStdLib, new ShellConsolePrinter());
-        defineFunctionProperties(TOP_COMMANDS, Global.class, ScriptableObject.DONTENUM);
+        defineFunctionProperties(this, TOP_COMMANDS, Global.class, ScriptableObject.DONTENUM);
 
         // Set up "environment" in the global scope to provide access to the
         // System environment variables.
@@ -261,7 +264,7 @@ public static void load(Context cx, Scriptable thisObj, Object[] args, Function
         for (Object arg : args) {
             String file = Context.toString(arg);
             try {
-                Main.processFile(cx, thisObj, file);
+                Main.processFile(cx, funObj.getDeclarationScope(), file);
             } catch (IOException ioex) {
                 String msg =
                         ToolErrorReporter.getMessage(
@@ -295,7 +298,8 @@ public static void defineClass(Context cx, Scriptable thisObj, Object[] args, Fu
         if (!Scriptable.class.isAssignableFrom(clazz)) {
             throw reportRuntimeError("msg.must.implement.Scriptable");
         }
-        ScriptableObject.defineClass(thisObj, (Class<? extends Scriptable>) clazz);
+        ScriptableObject.defineClass(
+                funObj.getDeclarationScope(), (Class<? extends Scriptable>) clazz);
     }
 
     /**
@@ -348,7 +352,7 @@ public static void serialize(Context cx, Scriptable thisObj, Object[] args, Func
         Object obj = args[0];
         String filename = Context.toString(args[1]);
         FileOutputStream fos = new FileOutputStream(filename);
-        Scriptable scope = ScriptableObject.getTopLevelScope(thisObj);
+        Scriptable scope = ScriptableObject.getTopLevelScope(funObj.getDeclarationScope());
         try (ScriptableOutputStream out = new ScriptableOutputStream(fos, scope)) {
             out.writeObject(obj);
         }
@@ -361,7 +365,7 @@ public static Object deserialize(Context cx, Scriptable thisObj, Object[] args,
         }
         String filename = Context.toString(args[0]);
         try (FileInputStream fis = new FileInputStream(filename)) {
-            Scriptable scope = ScriptableObject.getTopLevelScope(thisObj);
+            Scriptable scope = ScriptableObject.getTopLevelScope(funObj.getDeclarationScope());
             try (ObjectInputStream in = new ScriptableInputStream(fis, scope)) {
                 Object deserialized = in.readObject();
                 return Context.toObject(deserialized, scope);
diff --git a/rhino-tools/src/main/java/org/mozilla/javascript/tools/shell/Main.java b/rhino-tools/src/main/java/org/mozilla/javascript/tools/shell/Main.java
index dc5f93b3156..58c6e805f77 100644
--- a/rhino-tools/src/main/java/org/mozilla/javascript/tools/shell/Main.java
+++ b/rhino-tools/src/main/java/org/mozilla/javascript/tools/shell/Main.java
@@ -251,7 +251,7 @@ static Scriptable getScope(String path) {
                     uri = new File(path).toURI();
                 }
             }
-            return new ModuleScope(global, uri, null);
+            return ModuleScope.createModuleScope(global, uri, null);
         }
         return global;
     }
diff --git a/rhino/src/main/java/org/mozilla/javascript/AccessorSlot.java b/rhino/src/main/java/org/mozilla/javascript/AccessorSlot.java
index fe250a6923c..364324d4366 100644
--- a/rhino/src/main/java/org/mozilla/javascript/AccessorSlot.java
+++ b/rhino/src/main/java/org/mozilla/javascript/AccessorSlot.java
@@ -169,7 +169,7 @@ public Object getValue(Scriptable start) {
 
         @Override
         public Function asGetterFunction(String name, Scriptable scope) {
-            return member.asGetterFunction(name, scope);
+            return member.asGetterFunction(name);
         }
 
         @Override
@@ -246,7 +246,7 @@ public boolean setValue(Object value, Scriptable owner, Scriptable start) {
 
         @Override
         public Function asSetterFunction(String name, Scriptable scope) {
-            return member.asSetterFunction(name, scope);
+            return member.asSetterFunction(name);
         }
 
         @Override
diff --git a/rhino/src/main/java/org/mozilla/javascript/ArrayLikeAbstractOperations.java b/rhino/src/main/java/org/mozilla/javascript/ArrayLikeAbstractOperations.java
index b311e5aa893..e9a372b4238 100644
--- a/rhino/src/main/java/org/mozilla/javascript/ArrayLikeAbstractOperations.java
+++ b/rhino/src/main/java/org/mozilla/javascript/ArrayLikeAbstractOperations.java
@@ -137,10 +137,10 @@ public static Object coercibleIterativeMethod(
         Object callbackArg = args.length > 0 ? args[0] : Undefined.instance;
 
         Function f = getCallbackArg(cx, callbackArg);
-        Scriptable parent = ScriptableObject.getTopLevelScope(f);
+        TopLevel parent = ScriptableObject.getTopLevelScope(f);
         Scriptable thisArg;
         if (args.length < 2 || args[1] == null || args[1] == Undefined.instance) {
-            thisArg = parent;
+            thisArg = parent.getGlobalThis();
         } else {
             thisArg = ScriptRuntime.toObject(cx, scope, args[1]);
         }
@@ -339,7 +339,8 @@ public static Object reduceMethodWithLength(
             throw ScriptRuntime.notFunctionError(callbackArg);
         }
         Function f = (Function) callbackArg;
-        Scriptable parent = ScriptableObject.getTopLevelScope(f);
+        TopLevel parent = ScriptableObject.getTopLevelScope(f);
+        Scriptable globalThis = parent.getGlobalThis();
         // hack to serve both reduce and reduceRight with the same loop
         boolean movingLeft = operation == ReduceOperation.REDUCE;
         Object value = args.length > 1 ? args[1] : NOT_FOUND;
@@ -354,7 +355,7 @@ public static Object reduceMethodWithLength(
                 value = elem;
             } else {
                 Object[] innerArgs = {value, elem, index, o};
-                value = f.call(cx, parent, parent, innerArgs);
+                value = f.call(cx, parent, globalThis, innerArgs);
             }
         }
         if (value == NOT_FOUND) {
diff --git a/rhino/src/main/java/org/mozilla/javascript/BoundFunction.java b/rhino/src/main/java/org/mozilla/javascript/BoundFunction.java
index 2eaaf816801..f41c09ab6d5 100644
--- a/rhino/src/main/java/org/mozilla/javascript/BoundFunction.java
+++ b/rhino/src/main/java/org/mozilla/javascript/BoundFunction.java
@@ -109,11 +109,12 @@ Object[] getBoundArgs() {
 
     Scriptable getCallThis(Context cx, Scriptable scope) {
         Scriptable callThis = boundThis;
-        if (callThis == null && ScriptRuntime.hasTopCall(cx)) {
-            callThis = ScriptRuntime.getTopCallScope(cx);
-        }
         if (callThis == null) {
-            callThis = getTopLevelScope(scope);
+            if (ScriptRuntime.hasTopCall(cx)) {
+                callThis = ScriptRuntime.getTopCallScope(cx).getGlobalThis();
+            } else {
+                callThis = getTopLevelScope(scope).getGlobalThis();
+            }
         }
         return callThis;
     }
diff --git a/rhino/src/main/java/org/mozilla/javascript/ClassCache.java b/rhino/src/main/java/org/mozilla/javascript/ClassCache.java
index 484157d4262..48a58c90c99 100644
--- a/rhino/src/main/java/org/mozilla/javascript/ClassCache.java
+++ b/rhino/src/main/java/org/mozilla/javascript/ClassCache.java
@@ -77,12 +77,6 @@ public static ClassCache get(Scriptable scope) {
         if (cache == null) {
             // we expect this to not happen frequently, so computing top scope twice is acceptable
             var topScope = ScriptableObject.getTopLevelScope(scope);
-            if (!(topScope instanceof ScriptableObject)) {
-                // Note: it's originally a RuntimeException, the super class of
-                // IllegalArgumentException, so this will not break error catching
-                throw new IllegalArgumentException(
-                        "top scope have no associated ClassCache and cannot have ClassCache associated due to not being a ScriptableObject");
-            }
             cache = new ClassCache();
             cache.associate(((ScriptableObject) topScope));
         }
diff --git a/rhino/src/main/java/org/mozilla/javascript/ClassDescriptor.java b/rhino/src/main/java/org/mozilla/javascript/ClassDescriptor.java
index 17e6bef4413..c4a47ec0b81 100644
--- a/rhino/src/main/java/org/mozilla/javascript/ClassDescriptor.java
+++ b/rhino/src/main/java/org/mozilla/javascript/ClassDescriptor.java
@@ -107,9 +107,9 @@ private static class LambdaGetSetPropDesc extends PropDesc {
         @Override
         void makeProp(Context cx, Scriptable scope, ScriptableObject obj) {
             if (name instanceof String) {
-                obj.defineProperty(cx, (String) name, getter, setter, attributes);
+                obj.defineProperty(cx, scope, (String) name, getter, setter, attributes);
             } else {
-                obj.defineProperty(cx, (SymbolKey) name, getter, setter, attributes);
+                obj.defineProperty(cx, scope, (SymbolKey) name, getter, setter, attributes);
             }
         }
     }
diff --git a/rhino/src/main/java/org/mozilla/javascript/Context.java b/rhino/src/main/java/org/mozilla/javascript/Context.java
index a27f0d02113..0f78f1401f9 100644
--- a/rhino/src/main/java/org/mozilla/javascript/Context.java
+++ b/rhino/src/main/java/org/mozilla/javascript/Context.java
@@ -1052,7 +1052,7 @@ public static EvaluatorException reportRuntimeError(String message) {
      *
      * @return the initialized scope
      */
-    public final ScriptableObject initStandardObjects() {
+    public final TopLevel initStandardObjects() {
         return initStandardObjects(null, false);
     }
 
@@ -1095,7 +1095,7 @@ public final ScriptableObject initSafeStandardObjects() {
      * @return the initialized scope. The method returns the value of the scope argument if it is
      *     not null or newly allocated scope object which is an instance {@link ScriptableObject}.
      */
-    public final Scriptable initStandardObjects(ScriptableObject scope) {
+    public final TopLevel initStandardObjects(TopLevel scope) {
         return initStandardObjects(scope, false);
     }
 
@@ -1121,7 +1121,7 @@ public final Scriptable initStandardObjects(ScriptableObject scope) {
      * @return the initialized scope. The method returns the value of the scope argument if it is
      *     not null or newly allocated scope object which is an instance {@link ScriptableObject}.
      */
-    public final Scriptable initSafeStandardObjects(ScriptableObject scope) {
+    public final TopLevel initSafeStandardObjects(TopLevel scope) {
         return initSafeStandardObjects(scope, false);
     }
 
@@ -1148,7 +1148,7 @@ public final Scriptable initSafeStandardObjects(ScriptableObject scope) {
      *     not null or newly allocated scope object.
      * @since 1.4R3
      */
-    public ScriptableObject initStandardObjects(ScriptableObject scope, boolean sealed) {
+    public TopLevel initStandardObjects(TopLevel scope, boolean sealed) {
         return ScriptRuntime.initStandardObjects(this, scope, sealed);
     }
 
@@ -1181,7 +1181,7 @@ public ScriptableObject initStandardObjects(ScriptableObject scope, boolean seal
      *     not null or newly allocated scope object.
      * @since 1.7.6
      */
-    public ScriptableObject initSafeStandardObjects(ScriptableObject scope, boolean sealed) {
+    public TopLevel initSafeStandardObjects(TopLevel scope, boolean sealed) {
         return ScriptRuntime.initSafeStandardObjects(this, scope, sealed);
     }
 
@@ -1210,7 +1210,8 @@ public final Object evaluateString(
             Scriptable scope, String source, String sourceName, int lineno, Object securityDomain) {
         Script script = compileString(source, sourceName, lineno, securityDomain);
         if (script != null) {
-            return script.exec(this, scope, scope);
+            return script.exec(
+                    this, scope, ScriptableObject.getTopLevelScope(scope).getGlobalThis());
         }
         return null;
     }
@@ -2790,7 +2791,7 @@ public static boolean isCurrentContextStrict() {
     private boolean sealed;
     private Object sealKey;
 
-    Scriptable topCallScope;
+    TopLevel topCallScope;
     boolean isContinuationsTopCall;
     NativeCall currentActivationCall;
     private boolean isStrict;
diff --git a/rhino/src/main/java/org/mozilla/javascript/ES6Generator.java b/rhino/src/main/java/org/mozilla/javascript/ES6Generator.java
index 7bdb4ae6491..8b97fbe1213 100644
--- a/rhino/src/main/java/org/mozilla/javascript/ES6Generator.java
+++ b/rhino/src/main/java/org/mozilla/javascript/ES6Generator.java
@@ -18,7 +18,7 @@ public final class ES6Generator extends ScriptableObject {
     private State state = State.SUSPENDED_START;
     private Object delegee;
 
-    static ES6Generator init(ScriptableObject scope, boolean sealed) {
+    static ES6Generator init(TopLevel scope, boolean sealed) {
 
         ES6Generator prototype = new ES6Generator();
         if (scope != null) {
diff --git a/rhino/src/main/java/org/mozilla/javascript/ES6Iterator.java b/rhino/src/main/java/org/mozilla/javascript/ES6Iterator.java
index c871ea53510..52e426a63f0 100644
--- a/rhino/src/main/java/org/mozilla/javascript/ES6Iterator.java
+++ b/rhino/src/main/java/org/mozilla/javascript/ES6Iterator.java
@@ -17,7 +17,7 @@ public abstract class ES6Iterator extends ScriptableObject {
     public static final String RETURN_METHOD = "return";
 
     protected static void init(
-            ScriptableObject scope, boolean sealed, ScriptableObject prototype, String tag) {
+            TopLevel scope, boolean sealed, ScriptableObject prototype, String tag) {
         if (scope != null) {
             prototype.setParentScope(scope);
             prototype.setPrototype(getObjectPrototype(scope));
diff --git a/rhino/src/main/java/org/mozilla/javascript/FunctionObject.java b/rhino/src/main/java/org/mozilla/javascript/FunctionObject.java
index 47bf82ea1ea..83e41c501ea 100644
--- a/rhino/src/main/java/org/mozilla/javascript/FunctionObject.java
+++ b/rhino/src/main/java/org/mozilla/javascript/FunctionObject.java
@@ -14,7 +14,6 @@
 import java.lang.reflect.Member;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
-import org.mozilla.javascript.commonjs.module.ModuleScope;
 
 public class FunctionObject extends BaseFunction {
     private static final long serialVersionUID = -5332312783643935019L;
@@ -79,10 +78,10 @@ public class FunctionObject extends BaseFunction {
      */
     public FunctionObject(String name, Member methodOrConstructor, Scriptable scope) {
         if (methodOrConstructor instanceof Constructor) {
-            member = new MemberBox((Constructor<?>) methodOrConstructor);
+            member = new MemberBox(scope, (Constructor<?>) methodOrConstructor);
             isStatic = true; // well, doesn't take a 'this'
         } else {
-            member = new MemberBox((Method) methodOrConstructor);
+            member = new MemberBox(scope, (Method) methodOrConstructor);
             isStatic = member.isStatic();
         }
         String methodName = member.getName();
@@ -387,22 +386,8 @@ public Object call(Context cx, Scriptable scope, Scriptable thisObj, Object[] ar
                     thisObj = ((Delegator) thisObj).getDelegee();
                 }
                 if (!clazz.isInstance(thisObj)) {
-                    boolean compatible = false;
-                    if (thisObj == scope || thisObj instanceof ModuleScope) {
-                        Scriptable parentScope = getDeclarationScope();
-                        if (scope != parentScope) {
-                            // Call with dynamic scope for standalone function,
-                            // use parentScope as thisObj
-                            compatible = clazz.isInstance(parentScope);
-                            if (compatible) {
-                                thisObj = parentScope;
-                            }
-                        }
-                    }
-                    if (!compatible) {
-                        // Couldn't find an object to call this on.
-                        throw ScriptRuntime.typeErrorById("msg.incompat.call", functionName);
-                    }
+                    // Couldn't find an object to call this on.
+                    throw ScriptRuntime.typeErrorById("msg.incompat.call", functionName);
                 }
             }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/ImporterTopLevel.java b/rhino/src/main/java/org/mozilla/javascript/ImporterTopLevel.java
index 55b3726e60d..10684763269 100644
--- a/rhino/src/main/java/org/mozilla/javascript/ImporterTopLevel.java
+++ b/rhino/src/main/java/org/mozilla/javascript/ImporterTopLevel.java
@@ -47,16 +47,80 @@
 public class ImporterTopLevel extends TopLevel {
     private static final long serialVersionUID = -9095380847465315412L;
 
-    public ImporterTopLevel() {}
+    public static class ImporterGlobalThis extends TopLevel.GlobalThis {
+
+        private ImporterGlobalThis(boolean isTopScope) {
+            topScopeFlag = isTopScope;
+        }
+
+        @Override
+        public String getClassName() {
+            return topScopeFlag ? "global" : "JavaImporter";
+        }
+
+        @Override
+        public boolean has(String name, Scriptable start) {
+            return super.has(name, start) || getPackageProperty(name, start) != NOT_FOUND;
+        }
+
+        @Override
+        public Object get(String name, Scriptable start) {
+            Object result = super.get(name, start);
+            if (result != NOT_FOUND) return result;
+            result = getPackageProperty(name, start);
+            return result;
+        }
+
+        private Object getPackageProperty(String name, Scriptable start) {
+            Object result = NOT_FOUND;
+            Scriptable scope = start;
+            Object[] elements = getNativeJavaPackages(scope);
+            if (elements == null) {
+                return result;
+            }
+            for (Object element : elements) {
+                NativeJavaPackage p = (NativeJavaPackage) element;
+                Object v = p.getPkgProperty(name, start, false);
+                if (v != null && !(v instanceof NativeJavaPackage)) {
+                    if (result == NOT_FOUND) {
+                        result = v;
+                    } else {
+                        throw Context.reportRuntimeErrorById(
+                                "msg.ambig.import", result.toString(), v.toString());
+                    }
+                }
+            }
+
+            return result;
+        }
+
+        private final boolean topScopeFlag;
+    }
+
+    public ImporterTopLevel() {
+        this(true);
+    }
+
+    public ImporterTopLevel(boolean topLevel) {
+        super(new ImporterGlobalThis(topLevel));
+        topScopeFlag = topLevel;
+    }
 
     public ImporterTopLevel(Context cx) {
         this(cx, false);
     }
 
     public ImporterTopLevel(Context cx, boolean sealed) {
+        super(new ImporterGlobalThis(true));
+        topScopeFlag = true;
         initStandardObjects(cx, sealed);
     }
 
+    private ImporterTopLevel(ScriptableObject scope) {
+        super(scope);
+        topScopeFlag = true;
+    }
+
     @Override
     public String getClassName() {
         return topScopeFlag ? "global" : "JavaImporter";
@@ -91,7 +155,6 @@ public void initStandardObjects(Context cx, boolean sealed) {
         // Assume that Context.initStandardObjects initialize JavaImporter
         // property lazily so the above init call is not yet called
         cx.initStandardObjects(this, sealed);
-        topScopeFlag = true;
         // If seal is true then exportAsJSClass(cx, seal) would seal
         // this obj. Since this is scope as well, it would not allow
         // to add variables.
@@ -104,45 +167,6 @@ public void initStandardObjects(Context cx, boolean sealed) {
         delete("constructor");
     }
 
-    @Override
-    public boolean has(String name, Scriptable start) {
-        return super.has(name, start) || getPackageProperty(name, start) != NOT_FOUND;
-    }
-
-    @Override
-    public Object get(String name, Scriptable start) {
-        Object result = super.get(name, start);
-        if (result != NOT_FOUND) return result;
-        result = getPackageProperty(name, start);
-        return result;
-    }
-
-    private Object getPackageProperty(String name, Scriptable start) {
-        Object result = NOT_FOUND;
-        Scriptable scope = start;
-        if (topScopeFlag) {
-            scope = ScriptableObject.getTopLevelScope(scope);
-        }
-        Object[] elements = getNativeJavaPackages(scope);
-        if (elements == null) {
-            return result;
-        }
-        for (Object element : elements) {
-            NativeJavaPackage p = (NativeJavaPackage) element;
-            Object v = p.getPkgProperty(name, start, false);
-            if (v != null && !(v instanceof NativeJavaPackage)) {
-                if (result == NOT_FOUND) {
-                    result = v;
-                } else {
-                    throw Context.reportRuntimeErrorById(
-                            "msg.ambig.import", result.toString(), v.toString());
-                }
-            }
-        }
-
-        return result;
-    }
-
     private static Object[] getNativeJavaPackages(Scriptable scope) {
         // retrivee the native java packages stored in top scope.
         synchronized (scope) {
@@ -167,8 +191,11 @@ public void importPackage(Context cx, Scriptable thisObj, Object[] args, Functio
         js_importPackage(cx, funObj.getDeclarationScope(), this, args);
     }
 
+    // The result from the constructor needs to be an object rather
+    // than a scope, and then we need to work out to how make the
+    // import work on the correct thing.
     private static Scriptable js_construct(Context cx, Scriptable scope, Object[] args) {
-        ImporterTopLevel result = new ImporterTopLevel();
+        ImporterGlobalThis result = new ImporterGlobalThis(false);
         for (int i = 0; i != args.length; ++i) {
             Object arg = args[i];
             if (arg instanceof NativeJavaClass) {
@@ -208,6 +235,7 @@ private static Object js_importPackage(
             if (!(arg instanceof NativeJavaPackage)) {
                 throw Context.reportRuntimeErrorById("msg.not.pkg", Context.toString(arg));
             }
+
             importPackage((ScriptableObject) thisObj, (NativeJavaPackage) arg);
         }
         return Undefined.instance;
@@ -247,6 +275,24 @@ private static void importClass(Scriptable scope, NativeJavaClass cl) {
         scope.put(n, scope, cl);
     }
 
+    @Override
+    public ImporterGlobalThis getGlobalThis() {
+        return (ImporterGlobalThis) super.getGlobalThis();
+    }
+
+    public static TopLevel createIsolate(Context cx, TopLevel parent) {
+        var newGlobal = new ImporterGlobalThis(true);
+        newGlobal.setPrototype(parent.getGlobalThis());
+        newGlobal.setParentScope(null);
+        newGlobal.put("globalThis", newGlobal, newGlobal);
+        newGlobal.setAttributes("globalThis", ScriptableObject.DONTENUM);
+        var isolate = new ImporterTopLevel(newGlobal);
+        isolate.copyAssociatedValue(parent);
+        isolate.copyBuiltins(parent, false);
+        ImporterTopLevel.init(cx, isolate, false, true);
+        return isolate;
+    }
+
     private static final String AKEY = "importedPackages";
-    private boolean topScopeFlag;
+    private final boolean topScopeFlag;
 }
diff --git a/rhino/src/main/java/org/mozilla/javascript/JSScript.java b/rhino/src/main/java/org/mozilla/javascript/JSScript.java
index a026283bf56..be43cd8688c 100644
--- a/rhino/src/main/java/org/mozilla/javascript/JSScript.java
+++ b/rhino/src/main/java/org/mozilla/javascript/JSScript.java
@@ -31,6 +31,9 @@ JSCode<JSScript> getCode() {
     @Override
     public Object exec(Context cx, Scriptable scope, Scriptable thisObj) {
         Object ret;
+        if (thisObj instanceof TopLevel) {
+            thisObj = ((TopLevel) thisObj).getGlobalThis();
+        }
         if (!ScriptRuntime.hasTopCall(cx)) {
             // It will go through "call" path. but they are equivalent
             ret = ScriptRuntime.doTopCall(this, cx, scope, thisObj, descriptor.isStrict());
diff --git a/rhino/src/main/java/org/mozilla/javascript/LambdaConstructor.java b/rhino/src/main/java/org/mozilla/javascript/LambdaConstructor.java
index 42cd2a20b81..47fe08099fe 100644
--- a/rhino/src/main/java/org/mozilla/javascript/LambdaConstructor.java
+++ b/rhino/src/main/java/org/mozilla/javascript/LambdaConstructor.java
@@ -302,7 +302,12 @@ public void definePrototypeProperty(Context cx, Symbol key, ScriptableObject des
     public void definePrototypeProperty(
             Context cx, String name, ScriptableObject.LambdaGetterFunction getter, int attributes) {
         ScriptableObject proto = getPrototypeScriptable();
-        proto.defineProperty(cx, name, getter, null, attributes);
+        proto.defineProperty(cx, getDeclarationScope(), name, getter, null, attributes);
+    }
+
+    public void defineProperty(
+            Context cx, String name, LambdaGetterFunction getter, int attributes) {
+        defineProperty(cx, name, getter, null, attributes);
     }
 
     public void definePrototypeProperty(
@@ -313,7 +318,7 @@ public void definePrototypeProperty(
     public void definePrototypeProperty(
             Context cx, Symbol key, ScriptableObject.LambdaGetterFunction getter, int attributes) {
         ScriptableObject proto = getPrototypeScriptable();
-        proto.defineProperty(cx, key, getter, null, attributes);
+        proto.defineProperty(cx, getDeclarationScope(), key, getter, null, attributes);
     }
 
     /**
@@ -328,7 +333,7 @@ public void definePrototypeProperty(
             ScriptableObject.LambdaSetterFunction setter,
             int attributes) {
         ScriptableObject proto = getPrototypeScriptable();
-        proto.defineProperty(cx, name, getter, setter, attributes);
+        proto.defineProperty(cx, getDeclarationScope(), name, getter, setter, attributes);
     }
 
     public void definePrototypeProperty(
@@ -346,7 +351,7 @@ public void definePrototypeProperty(
             ScriptableObject.LambdaSetterFunction setter,
             int attributes) {
         ScriptableObject proto = getPrototypeScriptable();
-        proto.defineProperty(cx, key, getter, setter, attributes);
+        proto.defineProperty(cx, getDeclarationScope(), key, getter, setter, attributes);
     }
 
     public void definePrototypeProperty(
@@ -371,6 +376,15 @@ public void definePrototypeAlias(String name, String alias, int attributes) {
         proto.defineProperty(alias, val, attributes);
     }
 
+    public void defineProperty(
+            Context cx,
+            String name,
+            LambdaGetterFunction getter,
+            LambdaSetterFunction setter,
+            int attributes) {
+        defineProperty(cx, getDeclarationScope(), name, getter, setter, attributes);
+    }
+
     /**
      * Define a function property directly on the constructor that is implemented under the covers
      * by a LambdaFunction.
diff --git a/rhino/src/main/java/org/mozilla/javascript/MemberBox.java b/rhino/src/main/java/org/mozilla/javascript/MemberBox.java
index b1b5453c596..b583ad9300f 100644
--- a/rhino/src/main/java/org/mozilla/javascript/MemberBox.java
+++ b/rhino/src/main/java/org/mozilla/javascript/MemberBox.java
@@ -36,14 +36,18 @@ final class MemberBox implements Serializable {
     transient Function asSetterFunction;
     transient Object delegateTo;
 
+    private final Scriptable scope;
+
     private static final NullabilityDetector nullDetector =
             ScriptRuntime.loadOneServiceImplementation(NullabilityDetector.class);
 
-    MemberBox(Method method) {
+    MemberBox(Scriptable scope, Method method) {
+        this.scope = scope;
         init(method);
     }
 
-    MemberBox(Constructor<?> constructor) {
+    MemberBox(Scriptable scope, Constructor<?> constructor) {
+        this.scope = scope;
         init(constructor);
     }
 
@@ -156,7 +160,7 @@ boolean isSameSetterFunction(Object function) {
     }
 
     /** Function returned by calls to __lookupGetter__ */
-    Function asGetterFunction(final String name, final Scriptable scope) {
+    Function asGetterFunction(final String name) {
         // Note: scope is the scriptable this function is related to; therefore this function
         // is constant for this member box.
         // Because of this we can cache the function in the attribute
@@ -188,7 +192,7 @@ public String getFunctionName() {
     }
 
     /** Function returned by calls to __lookupSetter__ */
-    Function asSetterFunction(final String name, final Scriptable scope) {
+    Function asSetterFunction(final String name) {
         // Note: scope is the scriptable this function is related to; therefore this function
         // is constant for this member box.
         // Because of this we can cache the function in the attribute
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeArrayIterator.java b/rhino/src/main/java/org/mozilla/javascript/NativeArrayIterator.java
index 68f5ec9ba0f..adcc0fe1cf9 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeArrayIterator.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeArrayIterator.java
@@ -20,7 +20,7 @@ public enum ARRAY_ITERATOR_TYPE {
 
     private ARRAY_ITERATOR_TYPE type;
 
-    static void init(ScriptableObject scope, boolean sealed) {
+    static void init(TopLevel scope, boolean sealed) {
         ES6Iterator.init(scope, sealed, new NativeArrayIterator(), ITERATOR_TAG);
     }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeCollectionIterator.java b/rhino/src/main/java/org/mozilla/javascript/NativeCollectionIterator.java
index a4f6b6f66df..f617441314f 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeCollectionIterator.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeCollectionIterator.java
@@ -18,7 +18,7 @@ enum Type {
         BOTH
     }
 
-    static void init(ScriptableObject scope, String tag, boolean sealed) {
+    static void init(TopLevel scope, String tag, boolean sealed) {
         ES6Iterator.init(scope, sealed, new NativeCollectionIterator(tag), tag);
     }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeGenerator.java b/rhino/src/main/java/org/mozilla/javascript/NativeGenerator.java
index 586637832e4..fcc7610735c 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeGenerator.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeGenerator.java
@@ -17,7 +17,7 @@ public final class NativeGenerator extends IdScriptableObject {
 
     private static final Object GENERATOR_TAG = "Generator";
 
-    static NativeGenerator init(ScriptableObject scope, boolean sealed) {
+    static NativeGenerator init(TopLevel scope, boolean sealed) {
         // Generator
         // Can't use "NativeGenerator().exportAsJSClass" since we don't want
         // to define "Generator" as a constructor in the top-level scope.
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeGlobal.java b/rhino/src/main/java/org/mozilla/javascript/NativeGlobal.java
index 06d75757a45..8994c286c33 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeGlobal.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeGlobal.java
@@ -23,7 +23,7 @@
 public class NativeGlobal implements Serializable {
     static final long serialVersionUID = 6080442165748707530L;
 
-    public static void init(Context cx, Scriptable scope, boolean sealed) {
+    public static void init(Context cx, TopLevel scope, boolean sealed) {
         defineGlobalFunction(scope, sealed, "decodeURI", 1, NativeGlobal::js_decodeURI);
         defineGlobalFunction(
                 scope, sealed, "decodeURIComponent", 1, NativeGlobal::js_decodeURIComponent);
@@ -46,7 +46,13 @@ public static void init(Context cx, Scriptable scope, boolean sealed) {
                 scope, "Infinity", Double.POSITIVE_INFINITY, READONLY | DONTENUM | PERMANENT);
         ScriptableObject.defineProperty(
                 scope, "undefined", Undefined.instance, READONLY | DONTENUM | PERMANENT);
-        ScriptableObject.defineProperty(scope, "globalThis", scope, DONTENUM);
+        var globalThis = scope.getGlobalThis();
+
+        var obj = (Scriptable) scope.get("Object", scope);
+        var objProto = (Scriptable) obj.get("prototype", obj);
+        globalThis.setPrototype(objProto);
+
+        ScriptableObject.defineProperty(scope, "globalThis", globalThis, DONTENUM);
 
         /*
             Each error constructor gets its own Error object as a prototype,
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeIterator.java b/rhino/src/main/java/org/mozilla/javascript/NativeIterator.java
index ae70d9d5faf..c507c9dfb33 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeIterator.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeIterator.java
@@ -21,7 +21,7 @@ public final class NativeIterator extends ScriptableObject {
 
     private Object objectIterator;
 
-    static void init(Context cx, ScriptableObject scope, boolean sealed) {
+    static void init(Context cx, TopLevel scope, boolean sealed) {
         LambdaConstructor constructor =
                 new LambdaConstructor(
                         scope,
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeJavaMap.java b/rhino/src/main/java/org/mozilla/javascript/NativeJavaMap.java
index f01c2628725..6522544fd55 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeJavaMap.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeJavaMap.java
@@ -30,7 +30,7 @@ public class NativeJavaMap extends NativeJavaObject {
     private final TypeInfo keyType;
     private final TypeInfo valueType;
 
-    static void init(ScriptableObject scope, boolean sealed) {
+    static void init(TopLevel scope, boolean sealed) {
         NativeJavaMapIterator.init(scope, sealed);
     }
 
@@ -171,7 +171,7 @@ private static final class NativeJavaMapIterator extends ES6Iterator {
         private static final long serialVersionUID = 1L;
         private static final String ITERATOR_TAG = "JavaMapIterator";
 
-        static void init(ScriptableObject scope, boolean sealed) {
+        static void init(TopLevel scope, boolean sealed) {
             ES6Iterator.init(scope, sealed, new NativeJavaMapIterator(), ITERATOR_TAG);
         }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeJavaMethod.java b/rhino/src/main/java/org/mozilla/javascript/NativeJavaMethod.java
index 62ef1624579..770074f5ee4 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeJavaMethod.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeJavaMethod.java
@@ -53,7 +53,7 @@ public class NativeJavaMethod extends BaseFunction {
     }
 
     @Deprecated
-    public NativeJavaMethod(Method method, String name) {
+    public NativeJavaMethod(Scriptable scope, Method method, String name) {
         this(new ExecutableBox(method, TypeInfoFactory.GLOBAL, method.getDeclaringClass()), name);
     }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeJavaObject.java b/rhino/src/main/java/org/mozilla/javascript/NativeJavaObject.java
index e675bf10b6e..f0dc4d9ce49 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeJavaObject.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeJavaObject.java
@@ -35,7 +35,7 @@ public class NativeJavaObject implements Scriptable, SymbolScriptable, Wrapper,
 
     private static final long serialVersionUID = -6948590651130498591L;
 
-    static void init(ScriptableObject scope, boolean sealed) {
+    static void init(TopLevel scope, boolean sealed) {
         JavaIterableIterator.init(scope, sealed);
     }
 
@@ -923,7 +923,7 @@ private static final class JavaIterableIterator extends ES6Iterator {
         private static final long serialVersionUID = 1L;
         private static final String ITERATOR_TAG = "JavaIterableIterator";
 
-        static void init(ScriptableObject scope, boolean sealed) {
+        static void init(TopLevel scope, boolean sealed) {
             ES6Iterator.init(scope, sealed, new JavaIterableIterator(), ITERATOR_TAG);
         }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeMap.java b/rhino/src/main/java/org/mozilla/javascript/NativeMap.java
index 7a208935174..f9b17e544b7 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeMap.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeMap.java
@@ -208,7 +208,7 @@ private Object js_forEach(Context cx, Scriptable scope, Object arg1, Object arg2
             Scriptable thisObj = ScriptRuntime.toObjectOrNull(cx, arg2, scope);
 
             if (thisObj == null && !isStrict) {
-                thisObj = scope;
+                thisObj = ScriptableObject.getTopLevelScope(scope).getGlobalThis();
             }
             if (thisObj == null) {
                 thisObj = Undefined.SCRIPTABLE_UNDEFINED;
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativePromise.java b/rhino/src/main/java/org/mozilla/javascript/NativePromise.java
index b8a3a2cef57..2dc8d8887d3 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativePromise.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativePromise.java
@@ -72,9 +72,9 @@ private static Scriptable constructor(Context cx, Scriptable scope, Object[] arg
 
         Scriptable thisObj = Undefined.SCRIPTABLE_UNDEFINED;
         if (!cx.isStrictMode()) {
-            Scriptable tcs = cx.topCallScope;
+            TopLevel tcs = cx.topCallScope;
             if (tcs != null) {
-                thisObj = tcs;
+                thisObj = tcs.getGlobalThis();
             }
         }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeSet.java b/rhino/src/main/java/org/mozilla/javascript/NativeSet.java
index 74144c791cf..93d5fa17f89 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeSet.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeSet.java
@@ -202,7 +202,7 @@ private Object js_forEach(Context cx, Scriptable scope, Object arg1, Object arg2
             Scriptable thisObj = ScriptRuntime.toObjectOrNull(cx, arg2, scope);
 
             if (thisObj == null && !isStrict) {
-                thisObj = scope;
+                thisObj = ScriptableObject.getTopLevelScope(scope).getGlobalThis();
             }
             if (thisObj == null) {
                 thisObj = Undefined.SCRIPTABLE_UNDEFINED;
diff --git a/rhino/src/main/java/org/mozilla/javascript/NativeStringIterator.java b/rhino/src/main/java/org/mozilla/javascript/NativeStringIterator.java
index b55fe3fef59..56a32f283ba 100644
--- a/rhino/src/main/java/org/mozilla/javascript/NativeStringIterator.java
+++ b/rhino/src/main/java/org/mozilla/javascript/NativeStringIterator.java
@@ -10,7 +10,7 @@ public final class NativeStringIterator extends ES6Iterator {
     private static final long serialVersionUID = 1L;
     private static final String ITERATOR_TAG = "StringIterator";
 
-    static void init(ScriptableObject scope, boolean sealed) {
+    static void init(TopLevel scope, boolean sealed) {
         ES6Iterator.init(scope, sealed, new NativeStringIterator(), ITERATOR_TAG);
     }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/RegExpProxy.java b/rhino/src/main/java/org/mozilla/javascript/RegExpProxy.java
index c9abe507799..cead767b7e3 100644
--- a/rhino/src/main/java/org/mozilla/javascript/RegExpProxy.java
+++ b/rhino/src/main/java/org/mozilla/javascript/RegExpProxy.java
@@ -18,7 +18,7 @@ public interface RegExpProxy {
     public static final int RA_REPLACE_ALL = 3;
     public static final int RA_SEARCH = 4;
 
-    public void register(ScriptableObject scope, boolean sealed);
+    public void register(TopLevel scope, boolean sealed);
 
     public boolean isRegExp(Scriptable obj);
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/ScriptRuntime.java b/rhino/src/main/java/org/mozilla/javascript/ScriptRuntime.java
index 66c4e687571..d5cdf53dc7c 100644
--- a/rhino/src/main/java/org/mozilla/javascript/ScriptRuntime.java
+++ b/rhino/src/main/java/org/mozilla/javascript/ScriptRuntime.java
@@ -189,17 +189,16 @@ public static boolean isRhinoRuntimeType(Class<?> cl) {
                 || ScriptableClass.isAssignableFrom(cl));
     }
 
-    public static ScriptableObject initSafeStandardObjects(
-            Context cx, ScriptableObject scope, boolean sealed) {
+    public static TopLevel initSafeStandardObjects(Context cx, TopLevel scope, boolean sealed) {
         if (scope == null) {
-            scope = new NativeObject();
-        } else if (scope instanceof TopLevel) {
-            ((TopLevel) scope).clearCache();
+            scope = new TopLevel();
         }
 
-        scope.put("global", scope, scope);
+        scope.put("global", scope, scope.getGlobalThis());
 
+        scope.clearCache();
         scope.associateValue(LIBRARY_SCOPE_KEY, scope);
+
         new ClassCache().associate(scope);
         var typeFactory =
                 (androidApi >= 34 || androidApi < 0)
@@ -298,23 +297,20 @@ public static ScriptableObject initSafeStandardObjects(
             new LazilyLoadedCtor(scope, "Reflect", sealed, true, NativeReflect::init);
         }
 
-        if (scope instanceof TopLevel) {
-            ((TopLevel) scope).cacheBuiltins(scope, sealed);
-        }
+        scope.cacheBuiltins(sealed);
 
         return scope;
     }
 
-    private static void registerRegExp(Context cx, ScriptableObject scope, boolean sealed) {
+    private static void registerRegExp(Context cx, TopLevel scope, boolean sealed) {
         RegExpProxy regExpProxy = getRegExpProxy(cx);
         if (regExpProxy != null) {
             regExpProxy.register(scope, sealed);
         }
     }
 
-    public static ScriptableObject initStandardObjects(
-            Context cx, ScriptableObject scope, boolean sealed) {
-        ScriptableObject s = initSafeStandardObjects(cx, scope, sealed);
+    public static TopLevel initStandardObjects(Context cx, TopLevel scope, boolean sealed) {
+        TopLevel s = initSafeStandardObjects(cx, scope, sealed);
 
         // These depend on the legacy initialization behavior of the lazy loading mechanism
         new LazilyLoadedCtor(
@@ -3355,6 +3351,7 @@ private static Callable getValueFunctionAndThisInner(
             // nested functions should have top scope as their thisObj
             thisObj = ScriptableObject.getTopLevelScope(thisObj);
         }
+
         storeScriptable(cx, thisObj);
         return f;
     }
@@ -3396,6 +3393,7 @@ private static LookupResult getValueAndThisInner(
             // nested functions should have top scope as their thisObj
             thisObj = ScriptableObject.getTopLevelScope(thisObj);
         }
+
         return new LookupResult(f, thisObj, value);
     }
 
@@ -3543,7 +3541,7 @@ public static Scriptable getApplyOrCallThis(
             }
             if (callThis == null) {
                 // This covers the case of args[0] == (null|undefined) as well.
-                callThis = getTopCallScope(cx);
+                callThis = getTopCallScope(cx).getGlobalThis();
             }
         } else {
             // Spec-compliant behavior
@@ -3562,7 +3560,7 @@ public static Scriptable getApplyOrCallThis(
             boolean isFunctionStrict =
                     !(target instanceof JSFunction) || ((JSFunction) target).isStrict();
             if (missingCallThis && !isFunctionStrict) {
-                callThis = getTopCallScope(cx);
+                callThis = getTopCallScope(cx).getGlobalThis();
             }
         }
 
@@ -4868,8 +4866,8 @@ public static boolean hasTopCall(Context cx) {
         return (cx.topCallScope != null);
     }
 
-    public static Scriptable getTopCallScope(Context cx) {
-        Scriptable scope = cx.topCallScope;
+    public static TopLevel getTopCallScope(Context cx) {
+        var scope = cx.topCallScope;
         if (scope == null) {
             throw new IllegalStateException();
         }
@@ -5383,9 +5381,9 @@ public static void setObjectProtoAndParent(ScriptableObject object, Scriptable s
 
     public static void setBuiltinProtoAndParent(
             ScriptableObject object, Scriptable scope, TopLevel.Builtins type) {
-        scope = ScriptableObject.getTopLevelScope(scope);
-        object.setParentScope(scope);
-        object.setPrototype(TopLevel.getBuiltinPrototype(scope, type));
+        TopLevel top = ScriptableObject.getTopLevelScope(scope);
+        object.setParentScope(top);
+        object.setPrototype(TopLevel.getBuiltinPrototype(top, type));
     }
 
     public static void setBuiltinProtoAndParent(
@@ -6197,7 +6195,8 @@ public static final class LookupResult implements Serializable {
 
         LookupResult(Object result, Scriptable thisObj, Object name) {
             this.result = result;
-            this.thisObj = thisObj;
+            this.thisObj =
+                    thisObj instanceof TopLevel ? ((TopLevel) thisObj).getGlobalThis() : thisObj;
             this.name = name;
         }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/ScriptableObject.java b/rhino/src/main/java/org/mozilla/javascript/ScriptableObject.java
index 4bf1f69dbe8..1a41a570b1e 100644
--- a/rhino/src/main/java/org/mozilla/javascript/ScriptableObject.java
+++ b/rhino/src/main/java/org/mozilla/javascript/ScriptableObject.java
@@ -700,14 +700,14 @@ void addLazilyInitializedValue(Symbol key, int index, LazilyLoadedCtor init, int
      *     to regular property access.
      * @since 1.7.6
      */
-    public void setExternalArrayData(ExternalArrayData array) {
+    public void setExternalArrayData(Scriptable scope, ExternalArrayData array) {
         externalData = array;
 
         if (array == null) {
             delete("length");
         } else {
             // Define "length" to return whatever length the List gives us.
-            defineProperty("length", null, GET_ARRAY_LENGTH, null, READONLY | DONTENUM);
+            defineProperty(scope, "length", null, GET_ARRAY_LENGTH, null, READONLY | DONTENUM);
         }
     }
 
@@ -1228,7 +1228,7 @@ static <T extends Scriptable> BaseFunction buildClassCtor(
                         ScriptableObject.PERMANENT
                                 | ScriptableObject.DONTENUM
                                 | (setter != null ? 0 : ScriptableObject.READONLY);
-                ((ScriptableObject) proto).defineProperty(name, null, method, setter, attr);
+                ((ScriptableObject) proto).defineProperty(scope, name, null, method, setter, attr);
                 continue;
             }
 
@@ -1468,7 +1468,8 @@ public static void defineConstProperty(Scriptable destination, String propertyNa
      * @param attributes the attributes of the JavaScript property
      * @see org.mozilla.javascript.Scriptable#put(String, Scriptable, Object)
      */
-    public void defineProperty(String propertyName, Class<?> clazz, int attributes) {
+    public void defineProperty(
+            Scriptable scope, String propertyName, Class<?> clazz, int attributes) {
         int length = propertyName.length();
         if (length == 0) throw new IllegalArgumentException();
         char[] buf = new char[3 + length];
@@ -1485,7 +1486,8 @@ public void defineProperty(String propertyName, Class<?> clazz, int attributes)
         Method getter = FunctionObject.findSingleMethod(methods, getterName);
         Method setter = FunctionObject.findSingleMethod(methods, setterName);
         if (setter == null) attributes |= ScriptableObject.READONLY;
-        defineProperty(propertyName, null, getter, setter == null ? null : setter, attributes);
+        defineProperty(
+                scope, propertyName, null, getter, setter == null ? null : setter, attributes);
     }
 
     /**
@@ -1536,10 +1538,15 @@ public void defineProperty(String propertyName, Class<?> clazz, int attributes)
      * @param attributes the attributes of the JavaScript property
      */
     public void defineProperty(
-            String propertyName, Object delegateTo, Method getter, Method setter, int attributes) {
+            Scriptable scope,
+            String propertyName,
+            Object delegateTo,
+            Method getter,
+            Method setter,
+            int attributes) {
         MemberBox getterBox = null;
         if (getter != null) {
-            getterBox = new MemberBox(getter);
+            getterBox = new MemberBox(scope, getter);
 
             boolean delegatedForm;
             if (!Modifier.isStatic(getter.getModifiers())) {
@@ -1580,7 +1587,7 @@ public void defineProperty(
             if (setter.getReturnType() != Void.TYPE)
                 throw Context.reportRuntimeErrorById("msg.setter.return", setter.toString());
 
-            setterBox = new MemberBox(setter);
+            setterBox = new MemberBox(scope, setter);
 
             boolean delegatedForm;
             if (!Modifier.isStatic(setter.getModifiers())) {
@@ -2020,6 +2027,7 @@ public interface LambdaSetterFunction extends Serializable {
      */
     public void defineProperty(
             Context cx,
+            Scriptable scope,
             String name,
             LambdaGetterFunction getter,
             LambdaSetterFunction setter,
@@ -2027,17 +2035,23 @@ public void defineProperty(
         if (getter == null && setter == null)
             throw ScriptRuntime.typeError("at least one of {getter, setter} is required");
 
-        LambdaAccessorSlot newSlot = createLambdaAccessorSlot(name, 0, getter, setter, attributes);
+        LambdaAccessorSlot newSlot =
+                createLambdaAccessorSlot(name, 0, getter, setter, attributes, scope);
         replaceLambdaAccessorSlot(cx, name, newSlot);
     }
 
     public void defineProperty(
-            Context cx, String name, LambdaGetterFunction getter, int attributes) {
-        defineProperty(cx, name, getter, null, attributes);
+            Context cx,
+            Scriptable scope,
+            String name,
+            LambdaGetterFunction getter,
+            int attributes) {
+        defineProperty(cx, scope, name, getter, null, attributes);
     }
 
     public void defineProperty(
             Context cx,
+            Scriptable scope,
             Symbol key,
             LambdaGetterFunction getter,
             LambdaSetterFunction setter,
@@ -2045,7 +2059,8 @@ public void defineProperty(
         if (getter == null && setter == null)
             throw ScriptRuntime.typeError("at least one of {getter, setter} is required");
 
-        LambdaAccessorSlot newSlot = createLambdaAccessorSlot(key, 0, getter, setter, attributes);
+        LambdaAccessorSlot newSlot =
+                createLambdaAccessorSlot(key, 0, getter, setter, attributes, scope);
         replaceLambdaAccessorSlot(cx, key, newSlot);
     }
 
@@ -2089,10 +2104,11 @@ private LambdaAccessorSlot createLambdaAccessorSlot(
             int index,
             LambdaGetterFunction getter,
             LambdaSetterFunction setter,
-            int attributes) {
+            int attributes,
+            Scriptable scope) {
         LambdaAccessorSlot slot = new LambdaAccessorSlot(name, index);
-        slot.setGetter(this, getter);
-        slot.setSetter(this, setter);
+        slot.setGetter(scope, getter);
+        slot.setSetter(scope, setter);
         slot.setAttributes(attributes);
         return slot;
     }
@@ -2315,19 +2331,21 @@ protected static ScriptableObject ensureScriptableObjectButNotSymbol(Object arg)
      * constructed from the methods found, and are added to this object as properties with the given
      * names.
      *
+     * @param scope the declaration scope for the created function.
      * @param names the names of the Methods to add as function properties
      * @param clazz the class to search for the Methods
      * @param attributes the attributes of the new properties
      * @see org.mozilla.javascript.FunctionObject
      */
-    public void defineFunctionProperties(String[] names, Class<?> clazz, int attributes) {
+    public void defineFunctionProperties(
+            Scriptable scope, String[] names, Class<?> clazz, int attributes) {
         Method[] methods = FunctionObject.getMethodList(clazz);
         for (String name : names) {
             Method m = FunctionObject.findSingleMethod(methods, name);
             if (m == null) {
                 throw Context.reportRuntimeErrorById("msg.method.not.found", name, clazz.getName());
             }
-            FunctionObject f = new FunctionObject(name, m, this);
+            FunctionObject f = new FunctionObject(name, m, scope);
             defineProperty(name, f, attributes);
         }
     }
@@ -2398,11 +2416,14 @@ public static Scriptable getClassPrototype(Scriptable scope, String className) {
      * @param obj a JavaScript object
      * @return the corresponding global scope
      */
-    public static Scriptable getTopLevelScope(Scriptable obj) {
+    public static TopLevel getTopLevelScope(Scriptable obj) {
         for (; ; ) {
             Scriptable parent = obj.getParentScope();
             if (parent == null) {
-                return obj;
+                if (obj instanceof TopLevel) {
+                    return (TopLevel) obj;
+                }
+                throw new Error("Non-top level scope without parent");
             }
             obj = parent;
         }
@@ -2939,6 +2960,12 @@ public final Object getAssociatedValue(Object key) {
         return h.get(key);
     }
 
+    protected void copyAssociatedValue(ScriptableObject other) {
+        for (var e : other.associatedValues.entrySet()) {
+            associateValue(e.getKey(), e.getValue());
+        }
+    }
+
     /**
      * Get arbitrary application-specific value associated with the top scope of the given scope.
      * The method first calls {@link #getTopLevelScope(Scriptable scope)} and then searches the
@@ -2950,20 +2977,8 @@ public final Object getAssociatedValue(Object key) {
      * @see #getAssociatedValue(Object key)
      */
     public static Object getTopScopeValue(Scriptable scope, Object key) {
-        scope = ScriptableObject.getTopLevelScope(scope);
-        for (; ; ) {
-            if (scope instanceof ScriptableObject) {
-                ScriptableObject so = (ScriptableObject) scope;
-                Object value = so.getAssociatedValue(key);
-                if (value != null) {
-                    return value;
-                }
-            }
-            scope = scope.getPrototype();
-            if (scope == null) {
-                return null;
-            }
-        }
+        var topScope = ScriptableObject.getTopLevelScope(scope);
+        return topScope.getAssociatedValue(key);
     }
 
     /**
diff --git a/rhino/src/main/java/org/mozilla/javascript/SlotMapOwner.java b/rhino/src/main/java/org/mozilla/javascript/SlotMapOwner.java
index aebb932108b..2ee3a45929e 100644
--- a/rhino/src/main/java/org/mozilla/javascript/SlotMapOwner.java
+++ b/rhino/src/main/java/org/mozilla/javascript/SlotMapOwner.java
@@ -332,7 +332,7 @@ protected static SlotMap createSlotMap(int initialSize) {
         }
     }
 
-    final SlotMap getMap() {
+    SlotMap getMap() {
         return slotMap;
     }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/TopLevel.java b/rhino/src/main/java/org/mozilla/javascript/TopLevel.java
index 43834a060ff..1962d5a35b8 100644
--- a/rhino/src/main/java/org/mozilla/javascript/TopLevel.java
+++ b/rhino/src/main/java/org/mozilla/javascript/TopLevel.java
@@ -6,6 +6,9 @@
 
 package org.mozilla.javascript;
 
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.util.EnumMap;
 
 /**
@@ -26,8 +29,8 @@
  * <p>Calling {@link org.mozilla.javascript.Context#initStandardObjects()} with an instance of this
  * class as argument will automatically cache built-in classes after initialization. For other
  * setups involving top-level scopes that inherit global properties from their prototypes (e.g. with
- * dynamic scopes) embeddings should explicitly call {@link #cacheBuiltins(Scriptable, boolean)} to
- * initialize the class cache for each top-level scope.
+ * dynamic scopes) embeddings should explicitly call {@link #cacheBuiltins(boolean)} to initialize
+ * the class cache for each top-level scope.
  */
 public class TopLevel extends ScriptableObject {
 
@@ -99,12 +102,72 @@ enum NativeErrors {
         JavaException
     }
 
+    public static class GlobalThis extends ScriptableObject {
+
+        @Override
+        public String getClassName() {
+            return "global";
+        }
+    }
+
     private EnumMap<Builtins, BaseFunction> ctors;
     private EnumMap<NativeErrors, BaseFunction> errors;
+    private transient ScriptableObject globalThis;
+
+    private void writeObject(ObjectOutputStream out) throws IOException {
+        out.defaultWriteObject();
+        out.writeObject(globalThis);
+    }
+
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+        in.defaultReadObject();
+        globalThis = (ScriptableObject) in.readObject();
+    }
+
+    public TopLevel() {
+        this(new GlobalThis());
+    }
+
+    public TopLevel(ScriptableObject customGlobal) {
+        globalThis = customGlobal;
+    }
+
+    public static TopLevel createIsolate(TopLevel parent) {
+        var newGlobal = new NativeObject();
+        newGlobal.setPrototype(parent.getGlobalThis());
+        newGlobal.setParentScope(null);
+        var isolate = new TopLevel(newGlobal);
+        isolate.copyAssociatedValue(parent);
+        isolate.copyBuiltins(parent, false);
+        return isolate;
+    }
+
+    public static TopLevel createIsolate(TopLevel parent, ScriptableObject customGlobal) {
+        customGlobal.setParentScope(null);
+        customGlobal.setPrototype(parent.getGlobalThis());
+        var isolate = new TopLevel(customGlobal);
+        isolate.copyAssociatedValue(parent);
+        isolate.copyBuiltins(parent, false);
+        return isolate;
+    }
+
+    /**
+     * Only use this function if you have already set the customGlobal's prototype chain to point to
+     * this top level's global object. This should only be done if you know for certain that no
+     * other use will be made of this prototype chain.
+     */
+    public static TopLevel createIsolateCustomPrototypeChain(
+            TopLevel parent, ScriptableObject customGlobal) {
+        customGlobal.setParentScope(null);
+        var isolate = new TopLevel(customGlobal);
+        isolate.copyAssociatedValue(parent);
+        isolate.copyBuiltins(parent, false);
+        return isolate;
+    }
 
     @Override
     public String getClassName() {
-        return "global";
+        return "topLevel";
     }
 
     /**
@@ -113,8 +176,16 @@ public String getClassName() {
      * ScriptRuntime.initStandardObjects} if the scope argument is an instance of this class. It
      * only has to be called by the embedding if a top-level scope is not initialized through {@code
      * initStandardObjects()}.
+     *
+     * <p>This method is deprecated and kept for compatibility. Please use either {@link
+     * cacheBuiltins(boolean)} or {@link copyBuiltins(TopLevel, boolean)} instead.
      */
-    public void cacheBuiltins(Scriptable scope, boolean sealed) {
+    @Deprecated
+    public void cacheBuiltins(TopLevel scope, boolean sealed) {
+        cacheBuiltins(sealed);
+    }
+
+    public void cacheBuiltins(boolean sealed) {
         ctors = new EnumMap<>(Builtins.class);
         for (Builtins builtin : Builtins.values()) {
             Object value = ScriptableObject.getProperty(this, builtin.name());
@@ -124,8 +195,7 @@ public void cacheBuiltins(Scriptable scope, boolean sealed) {
                 // Handle weird situation of "GeneratorFunction" being a real constructor
                 // which is never registered in the top-level scope
                 ctors.put(
-                        builtin,
-                        (BaseFunction) BaseFunction.initAsGeneratorFunction(scope, sealed));
+                        builtin, (BaseFunction) BaseFunction.initAsGeneratorFunction(this, sealed));
             }
         }
         errors = new EnumMap<>(NativeErrors.class);
@@ -137,6 +207,11 @@ public void cacheBuiltins(Scriptable scope, boolean sealed) {
         }
     }
 
+    public void copyBuiltins(TopLevel other, boolean sealed) {
+        ctors = other.ctors;
+        errors = other.errors;
+    }
+
     /** Clears the cache; this is necessary, when standard objects are reinitialized. */
     void clearCache() {
         ctors = null;
@@ -207,15 +282,13 @@ static Function getNativeErrorCtor(Context cx, Scriptable scope, NativeErrors ty
      * @param type the built-in type
      * @return the built-in prototype
      */
-    public static Scriptable getBuiltinPrototype(Scriptable scope, Builtins type) {
+    public static Scriptable getBuiltinPrototype(TopLevel scope, Builtins type) {
         // must be called with top level scope
-        assert scope.getParentScope() == null;
-        if (scope instanceof TopLevel) {
-            Scriptable result = ((TopLevel) scope).getBuiltinPrototype(type);
-            if (result != null) {
-                return result;
-            }
+        Scriptable result = ((TopLevel) scope).getBuiltinPrototype(type);
+        if (result != null) {
+            return result;
         }
+
         // fall back to normal prototype lookup
         String typeName;
         if (type == Builtins.GeneratorFunction) {
@@ -231,8 +304,7 @@ public static Scriptable getBuiltinPrototype(Scriptable scope, Builtins type) {
 
     /**
      * Get the cached built-in object constructor from this scope with the given {@code type}.
-     * Returns null if {@link #cacheBuiltins(Scriptable, boolean)} has not been called on this
-     * object.
+     * Returns null if {@link #cacheBuiltins(boolean)} has not been called on this object.
      *
      * @param type the built-in type
      * @return the built-in constructor
@@ -243,7 +315,7 @@ public BaseFunction getBuiltinCtor(Builtins type) {
 
     /**
      * Get the cached native error constructor from this scope with the given {@code type}. Returns
-     * null if {@link #cacheBuiltins(Scriptable, boolean)} has not been called on this object.
+     * null if {@link #cacheBuiltins(boolean)} has not been called on this object.
      *
      * @param type the native error type
      * @return the native error constructor
@@ -254,7 +326,7 @@ BaseFunction getNativeErrorCtor(NativeErrors type) {
 
     /**
      * Get the cached built-in object prototype from this scope with the given {@code type}. Returns
-     * null if {@link #cacheBuiltins(Scriptable, boolean)} has not been called on this object.
+     * null if {@link #cacheBuiltins(boolean)} has not been called on this object.
      *
      * @param type the built-in type
      * @return the built-in prototype
@@ -264,4 +336,91 @@ public Scriptable getBuiltinPrototype(Builtins type) {
         Object proto = func != null ? func.getPrototypeProperty() : null;
         return proto instanceof Scriptable ? (Scriptable) proto : null;
     }
+
+    public ScriptableObject getGlobalThis() {
+        return globalThis;
+    }
+
+    @Override
+    public Object get(String name, Scriptable start) {
+        var res = super.get(name, start);
+        if (res != NOT_FOUND) {
+            return res;
+        }
+        return ScriptableObject.getProperty(globalThis, name);
+    }
+
+    @Override
+    public void put(String name, Scriptable start, Object value) {
+        ScriptableObject.putProperty(globalThis, name, value);
+    }
+
+    @Override
+    public boolean has(String name, Scriptable start) {
+        return super.has(name, start) || ScriptableObject.hasProperty(globalThis, name);
+    }
+
+    @Override
+    public void delete(String name) {
+        globalThis.delete(name);
+    }
+
+    @Override
+    public void sealObject() {
+        globalThis.sealObject();
+        super.sealObject();
+    }
+
+    @Override
+    public void defineProperty(String propertyName, Object value, int attributes) {
+        globalThis.defineProperty(propertyName, value, attributes);
+    }
+
+    @Override
+    void addLazilyInitializedValue(String name, int index, LazilyLoadedCtor init, int attributes) {
+        globalThis.addLazilyInitializedValue(name, index, init, attributes);
+    }
+
+    @Override
+    public void setAttributes(String name, int attributes) {
+        if (super.get(name, this) != NOT_FOUND) {
+            super.setAttributes(name, attributes);
+        } else {
+            globalThis.setAttributes(name, attributes);
+        }
+    }
+
+    @Override
+    public int getAttributes(String name) {
+        if (super.get(name, this) != NOT_FOUND) {
+            return super.getAttributes(name);
+        } else {
+            return globalThis.getAttributes(name);
+        }
+    }
+
+    // Technically this is wrong, but there are currently tests that
+    // depend const variable being defined on globalThis.
+    //
+    // In a compliant implementation const declarations should bind
+    // the values on the global scope but not on the global object.
+
+    @Override
+    public boolean isConst(String name) {
+        if (super.get(name, this) != NOT_FOUND) {
+            return super.isConst(name);
+        } else {
+            return globalThis.isConst(name);
+        }
+    }
+
+    @Override
+    public void putConst(String name, Scriptable start, Object value) {
+        globalThis.putConst(name, globalThis, value);
+    }
+
+    @Override
+    public void defineConst(String name, Scriptable start) {
+        globalThis.defineConst(name, globalThis);
+    }
 }
diff --git a/rhino/src/main/java/org/mozilla/javascript/commonjs/module/ModuleScope.java b/rhino/src/main/java/org/mozilla/javascript/commonjs/module/ModuleScope.java
index 8be9e77a329..791d674a3e5 100644
--- a/rhino/src/main/java/org/mozilla/javascript/commonjs/module/ModuleScope.java
+++ b/rhino/src/main/java/org/mozilla/javascript/commonjs/module/ModuleScope.java
@@ -6,22 +6,27 @@
 
 import java.net.URI;
 import org.mozilla.javascript.Scriptable;
+import org.mozilla.javascript.ScriptableObject;
 import org.mozilla.javascript.TopLevel;
 
 /**
  * A top-level module scope. This class provides methods to retrieve the module's source and base
  * URIs in order to resolve relative module IDs and check sandbox constraints.
  */
-public class ModuleScope extends TopLevel {
+public class ModuleScope extends ScriptableObject {
     private static final long serialVersionUID = 1L;
     private final URI uri;
     private final URI base;
 
-    public ModuleScope(Scriptable prototype, URI uri, URI base) {
+    private ModuleScope(URI uri, URI base) {
         this.uri = uri;
         this.base = base;
-        setPrototype(prototype);
-        cacheBuiltins(prototype, false);
+    }
+
+    public static ScriptableObject createModuleScope(TopLevel global, URI uri, URI base) {
+        var moduleScope = new ModuleScope(uri, base);
+        moduleScope.setParentScope(global);
+        return moduleScope;
     }
 
     public URI getUri() {
@@ -31,4 +36,21 @@ public URI getUri() {
     public URI getBase() {
         return base;
     }
+
+    @Override
+    public String getClassName() {
+        return "module";
+    }
+
+    /** Search up the chain of scopes to find a module scope. */
+    public static ModuleScope findModuleScope(Scriptable scope) {
+        Scriptable current = scope;
+        while (current != null) {
+            if (current instanceof ModuleScope) {
+                return (ModuleScope) current;
+            }
+            current = current.getParentScope();
+        }
+        return null;
+    }
 }
diff --git a/rhino/src/main/java/org/mozilla/javascript/commonjs/module/Require.java b/rhino/src/main/java/org/mozilla/javascript/commonjs/module/Require.java
index 5169c2df5b4..8ce6d32d582 100644
--- a/rhino/src/main/java/org/mozilla/javascript/commonjs/module/Require.java
+++ b/rhino/src/main/java/org/mozilla/javascript/commonjs/module/Require.java
@@ -16,6 +16,8 @@
 import org.mozilla.javascript.ScriptRuntime;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
+import org.mozilla.javascript.Undefined;
 
 /**
  * Implements the require() function as defined by <a
@@ -44,7 +46,7 @@
 public class Require extends BaseFunction {
     private static final long serialVersionUID = 1L;
     private final ModuleScriptProvider moduleScriptProvider;
-    private final Scriptable nativeScope;
+    private final TopLevel nativeScope;
     private final Scriptable paths;
     private final boolean sandboxed;
     private final Script preExec;
@@ -79,7 +81,7 @@ public class Require extends BaseFunction {
      */
     public Require(
             Context cx,
-            Scriptable nativeScope,
+            TopLevel nativeScope,
             ModuleScriptProvider moduleScriptProvider,
             Script preExec,
             Script postExec,
@@ -175,12 +177,18 @@ public Object call(Context cx, Scriptable scope, Scriptable thisObj, Object[] ar
         if (args == null || args.length < 1) {
             throw ScriptRuntime.throwError(cx, scope, "require() needs one argument");
         }
+        // Top scope from the point of view of the callee
+        TopLevel topScope = ScriptableObject.getTopLevelScope(scope);
+        if (thisObj == null || Undefined.isUndefined(thisObj)) {
+            thisObj = topScope.getGlobalThis();
+        }
+        ModuleScope moduleScope = ModuleScope.findModuleScope(scope);
 
         String id = (String) Context.jsToJava(args[0], String.class);
         URI uri = null;
         URI base = null;
         if (id.startsWith("./") || id.startsWith("../")) {
-            if (!(thisObj instanceof ModuleScope)) {
+            if (moduleScope == null) {
                 throw ScriptRuntime.throwError(
                         cx,
                         scope,
@@ -189,7 +197,6 @@ public Object call(Context cx, Scriptable scope, Scriptable thisObj, Object[] ar
                                 + "\" when require() is used outside of a module");
             }
 
-            ModuleScope moduleScope = (ModuleScope) thisObj;
             base = moduleScope.getBase();
             URI current = moduleScope.getUri();
             uri = current.resolve(id);
@@ -313,7 +320,7 @@ private Scriptable executeModuleScript(
         if (!sandboxed) {
             defineReadOnlyProperty(moduleObject, "uri", uri.toString());
         }
-        final Scriptable executionScope = new ModuleScope(nativeScope, uri, base);
+        final Scriptable executionScope = ModuleScope.createModuleScope(nativeScope, uri, base);
         // Set this so it can access the global JS environment objects.
         // This means we're currently using the "MGN" approach (ModuleScript
         // with Global Natives) as specified here:
diff --git a/rhino/src/main/java/org/mozilla/javascript/commonjs/module/RequireBuilder.java b/rhino/src/main/java/org/mozilla/javascript/commonjs/module/RequireBuilder.java
index 3919b79160a..697cf5ac91f 100644
--- a/rhino/src/main/java/org/mozilla/javascript/commonjs/module/RequireBuilder.java
+++ b/rhino/src/main/java/org/mozilla/javascript/commonjs/module/RequireBuilder.java
@@ -8,6 +8,7 @@
 import org.mozilla.javascript.Context;
 import org.mozilla.javascript.Script;
 import org.mozilla.javascript.Scriptable;
+import org.mozilla.javascript.TopLevel;
 
 /**
  * A builder for {@link Require} instances. Useful when you're creating many instances of {@link
@@ -85,7 +86,7 @@ public RequireBuilder setSandboxed(boolean sandboxed) {
      * @param globalScope the global scope containing the JS standard natives.
      * @return a new Require instance.
      */
-    public Require createRequire(Context cx, Scriptable globalScope) {
+    public Require createRequire(Context cx, TopLevel globalScope) {
         return new Require(cx, globalScope, moduleScriptProvider, preExec, postExec, sandboxed);
     }
 }
diff --git a/rhino/src/main/java/org/mozilla/javascript/lc/type/TypeInfoFactory.java b/rhino/src/main/java/org/mozilla/javascript/lc/type/TypeInfoFactory.java
index 91bd41e99a1..06cdaf84a22 100644
--- a/rhino/src/main/java/org/mozilla/javascript/lc/type/TypeInfoFactory.java
+++ b/rhino/src/main/java/org/mozilla/javascript/lc/type/TypeInfoFactory.java
@@ -23,6 +23,7 @@
 import java.util.function.Supplier;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.lc.type.impl.factory.ClassValueCacheFactory;
 import org.mozilla.javascript.lc.type.impl.factory.LegacyCacheFactory;
 
@@ -348,7 +349,7 @@ static TypeInfo matchPredefined(Class<?> clazz) {
      * @throws IllegalArgumentException if provided scope is not top scope
      * @see #get(Scriptable scope)
      */
-    default TypeInfoFactory associate(ScriptableObject topScope) {
+    default TypeInfoFactory associate(TopLevel topScope) {
         if (topScope.getParentScope() != null) {
             throw new IllegalArgumentException("provided scope not top scope");
         }
diff --git a/rhino/src/main/java/org/mozilla/javascript/regexp/NativeRegExpStringIterator.java b/rhino/src/main/java/org/mozilla/javascript/regexp/NativeRegExpStringIterator.java
index 170ec373549..91ffa82835a 100644
--- a/rhino/src/main/java/org/mozilla/javascript/regexp/NativeRegExpStringIterator.java
+++ b/rhino/src/main/java/org/mozilla/javascript/regexp/NativeRegExpStringIterator.java
@@ -10,7 +10,7 @@
 import org.mozilla.javascript.ES6Iterator;
 import org.mozilla.javascript.ScriptRuntime;
 import org.mozilla.javascript.Scriptable;
-import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.Undefined;
 
 // See ECMAScript spec 22.2.9.1
@@ -25,7 +25,7 @@ public final class NativeRegExpStringIterator extends ES6Iterator {
     private boolean nextDone;
     private Object next = null;
 
-    public static void init(ScriptableObject scope, boolean sealed) {
+    public static void init(TopLevel scope, boolean sealed) {
         ES6Iterator.init(scope, sealed, new NativeRegExpStringIterator(), ITERATOR_TAG);
     }
 
diff --git a/rhino/src/main/java/org/mozilla/javascript/regexp/RegExpImpl.java b/rhino/src/main/java/org/mozilla/javascript/regexp/RegExpImpl.java
index 7f6b0d57f58..54093c291e5 100644
--- a/rhino/src/main/java/org/mozilla/javascript/regexp/RegExpImpl.java
+++ b/rhino/src/main/java/org/mozilla/javascript/regexp/RegExpImpl.java
@@ -14,13 +14,14 @@
 import org.mozilla.javascript.ScriptRuntime;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.Undefined;
 
 /** */
 public class RegExpImpl implements RegExpProxy {
 
     @Override
-    public void register(ScriptableObject scope, boolean sealed) {
+    public void register(TopLevel scope, boolean sealed) {
         NativeRegExpStringIterator.init(scope, sealed);
         new LazilyLoadedCtor(scope, "RegExp", sealed, true, NativeRegExp::init);
     }
diff --git a/rhino/src/test/java/org/mozilla/javascript/NullabilityDetectorTest.java b/rhino/src/test/java/org/mozilla/javascript/NullabilityDetectorTest.java
index 32a08cb655f..4beda535640 100644
--- a/rhino/src/test/java/org/mozilla/javascript/NullabilityDetectorTest.java
+++ b/rhino/src/test/java/org/mozilla/javascript/NullabilityDetectorTest.java
@@ -11,37 +11,43 @@
 public class NullabilityDetectorTest {
     @Test
     public void testNullableDetectorForMethodWithoutArgs() {
-        MemberBox memberBox = new MemberBox(getTestClassMethod("function1"));
+        var scope = new TopLevel();
+        MemberBox memberBox = new MemberBox(scope, getTestClassMethod("function1"));
         assertNullabilityMatch(memberBox.getArgNullability());
     }
 
     @Test
     public void testNullableDetectorForMethodWithOneArg() {
-        MemberBox memberBox = new MemberBox(getTestClassMethod("function2"));
+        var scope = new TopLevel();
+        MemberBox memberBox = new MemberBox(scope, getTestClassMethod("function2"));
         assertNullabilityMatch(memberBox.getArgNullability(), true);
     }
 
     @Test
     public void testNullableDetectorForMethodWithSeveralArgs() {
-        MemberBox memberBox = new MemberBox(getTestClassMethod("function3"));
+        var scope = new TopLevel();
+        MemberBox memberBox = new MemberBox(scope, getTestClassMethod("function3"));
         assertNullabilityMatch(memberBox.getArgNullability(), true, true, true, true);
     }
 
     @Test
     public void testNullableDetectorForConstructorWithoutArgs() {
-        MemberBox memberBox = new MemberBox(getTestClassConstructor(0));
+        var scope = new TopLevel();
+        MemberBox memberBox = new MemberBox(scope, getTestClassConstructor(0));
         assertNullabilityMatch(memberBox.getArgNullability());
     }
 
     @Test
     public void testNullableDetectorForConstructorWithOneArg() {
-        MemberBox memberBox = new MemberBox(getTestClassConstructor(1));
+        var scope = new TopLevel();
+        MemberBox memberBox = new MemberBox(scope, getTestClassConstructor(1));
         assertNullabilityMatch(memberBox.getArgNullability(), true);
     }
 
     @Test
     public void testNullableDetectorForConstructorWithSeveralArgs() {
-        MemberBox memberBox = new MemberBox(getTestClassConstructor(4));
+        var scope = new TopLevel();
+        MemberBox memberBox = new MemberBox(scope, getTestClassConstructor(4));
         assertNullabilityMatch(memberBox.getArgNullability(), true, false, true, false);
     }
 
diff --git a/rhino/src/test/java/org/mozilla/javascript/SuperTest.java b/rhino/src/test/java/org/mozilla/javascript/SuperTest.java
index e1a698a6664..8d4198d7d6f 100644
--- a/rhino/src/test/java/org/mozilla/javascript/SuperTest.java
+++ b/rhino/src/test/java/org/mozilla/javascript/SuperTest.java
@@ -372,7 +372,10 @@ public void error(
                                             int line,
                                             String lineSource,
                                             int lineOffset) {
-                                        fail("should not have been called");
+                                        fail(
+                                                String.format(
+                                                        "should not have been called but was with %s",
+                                                        message));
                                     }
 
                                     @Override
@@ -382,7 +385,10 @@ public EvaluatorException runtimeError(
                                             int line,
                                             String lineSource,
                                             int lineOffset) {
-                                        fail("should not have been called");
+                                        fail(
+                                                String.format(
+                                                        "should not have been called but was with %s",
+                                                        message));
                                         return null;
                                     }
                                 });
diff --git a/rhino/src/test/java/org/mozilla/javascript/tests/Bug685403Test.java b/rhino/src/test/java/org/mozilla/javascript/tests/Bug685403Test.java
index 9c9f49748a2..db2b703deb6 100755
--- a/rhino/src/test/java/org/mozilla/javascript/tests/Bug685403Test.java
+++ b/rhino/src/test/java/org/mozilla/javascript/tests/Bug685403Test.java
@@ -53,7 +53,8 @@ public void test() {
         source += "state";
 
         String[] functions = new String[] {"continuation"};
-        scope.defineFunctionProperties(functions, Bug685403Test.class, ScriptableObject.DONTENUM);
+        scope.defineFunctionProperties(
+                scope, functions, Bug685403Test.class, ScriptableObject.DONTENUM);
 
         Object state = null;
         Script script = cx.compileString(source, "", 1, null);
diff --git a/rhino/src/test/java/org/mozilla/javascript/tests/Bug783797Test.java b/rhino/src/test/java/org/mozilla/javascript/tests/Bug783797Test.java
index a0581122176..0a05079a953 100755
--- a/rhino/src/test/java/org/mozilla/javascript/tests/Bug783797Test.java
+++ b/rhino/src/test/java/org/mozilla/javascript/tests/Bug783797Test.java
@@ -13,6 +13,7 @@
 import org.mozilla.javascript.ContextAction;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 
 /**
  * @author André Bargull
@@ -513,13 +514,15 @@ public void returnThis() {
                             @Override
                             public void run(
                                     Context cx, ScriptableObject scope1, ScriptableObject scope2) {
-                                assertSame(scope2, eval(cx, scope2, "test()"));
-                                assertSame(scope2, eval(cx, scope2, "test.call(null)"));
-                                assertSame(scope2, eval(cx, scope1, "scope2.test()"));
-                                assertSame(scope1, eval(cx, scope1, "scope2.test.call(null)"));
-                                assertSame(scope1, eval(cx, scope1, "var t=scope2.test; t()"));
+                                var globalThis1 = ((TopLevel) scope1).getGlobalThis();
+                                var globalThis2 = ((TopLevel) scope2).getGlobalThis();
+                                assertSame(globalThis2, eval(cx, scope2, "test()"));
+                                assertSame(globalThis2, eval(cx, scope2, "test.call(null)"));
+                                assertSame(globalThis2, eval(cx, scope1, "scope2.test()"));
+                                assertSame(globalThis1, eval(cx, scope1, "scope2.test.call(null)"));
+                                assertSame(globalThis1, eval(cx, scope1, "var t=scope2.test; t()"));
                                 assertSame(
-                                        scope1,
+                                        globalThis1,
                                         eval(cx, scope1, "var t=scope2.test; t.call(null)"));
                             }
                         }));
@@ -535,13 +538,14 @@ public void returnThisNested() {
                             @Override
                             public void run(
                                     Context cx, ScriptableObject scope1, ScriptableObject scope2) {
-                                assertSame(scope2, eval(cx, scope2, "test()"));
-                                assertSame(scope2, eval(cx, scope2, "test.call(null)"));
-                                assertSame(scope2, eval(cx, scope1, "scope2.test()"));
-                                assertSame(scope2, eval(cx, scope1, "scope2.test.call(null)"));
-                                assertSame(scope2, eval(cx, scope1, "var t=scope2.test; t()"));
+                                var globalThis = ((TopLevel) scope2).getGlobalThis();
+                                assertSame(globalThis, eval(cx, scope2, "test()"));
+                                assertSame(globalThis, eval(cx, scope2, "test.call(null)"));
+                                assertSame(globalThis, eval(cx, scope1, "scope2.test()"));
+                                assertSame(globalThis, eval(cx, scope1, "scope2.test.call(null)"));
+                                assertSame(globalThis, eval(cx, scope1, "var t=scope2.test; t()"));
                                 assertSame(
-                                        scope2,
+                                        globalThis,
                                         eval(cx, scope1, "var t=scope2.test; t.call(null)"));
                             }
                         }));
@@ -557,24 +561,29 @@ public void returnThisNestedCall() {
                             @Override
                             public void run(
                                     Context cx, ScriptableObject scope1, ScriptableObject scope2) {
-                                assertSame(scope2, eval(cx, scope2, "test()"));
-                                assertSame(scope2, eval(cx, scope2, "test(null)"));
-                                assertSame(scope2, eval(cx, scope2, "test.call(null)"));
-                                assertSame(scope2, eval(cx, scope2, "test.call(null, null)"));
-
-                                assertSame(scope1, eval(cx, scope1, "scope2.test()"));
-                                assertSame(scope1, eval(cx, scope1, "scope2.test(null)"));
-                                assertSame(scope1, eval(cx, scope1, "scope2.test.call(null)"));
+                                var globalThis1 = ((TopLevel) scope1).getGlobalThis();
+                                var globalThis2 = ((TopLevel) scope2).getGlobalThis();
+                                assertSame(globalThis2, eval(cx, scope2, "test()"));
+                                assertSame(globalThis2, eval(cx, scope2, "test(null)"));
+                                assertSame(globalThis2, eval(cx, scope2, "test.call(null)"));
+                                assertSame(globalThis2, eval(cx, scope2, "test.call(null, null)"));
+
+                                assertSame(globalThis1, eval(cx, scope1, "scope2.test()"));
+                                assertSame(globalThis1, eval(cx, scope1, "scope2.test(null)"));
+                                assertSame(globalThis1, eval(cx, scope1, "scope2.test.call(null)"));
                                 assertSame(
-                                        scope1, eval(cx, scope1, "scope2.test.call(null, null)"));
+                                        globalThis1,
+                                        eval(cx, scope1, "scope2.test.call(null, null)"));
 
-                                assertSame(scope1, eval(cx, scope1, "var t=scope2.test; t()"));
-                                assertSame(scope1, eval(cx, scope1, "var t=scope2.test; t(null)"));
+                                assertSame(globalThis1, eval(cx, scope1, "var t=scope2.test; t()"));
                                 assertSame(
-                                        scope1,
+                                        globalThis1,
+                                        eval(cx, scope1, "var t=scope2.test; t(null)"));
+                                assertSame(
+                                        globalThis1,
                                         eval(cx, scope1, "var t=scope2.test; t.call(null)"));
                                 assertSame(
-                                        scope1,
+                                        globalThis1,
                                         eval(cx, scope1, "var t=scope2.test; t.call(null, null)"));
                             }
                         }));
diff --git a/rhino/src/test/java/org/mozilla/javascript/tests/ConsStringTest.java b/rhino/src/test/java/org/mozilla/javascript/tests/ConsStringTest.java
index 98ed765984a..11d651fdc2e 100644
--- a/rhino/src/test/java/org/mozilla/javascript/tests/ConsStringTest.java
+++ b/rhino/src/test/java/org/mozilla/javascript/tests/ConsStringTest.java
@@ -63,7 +63,8 @@ public void doNotLeakConsStringIntoSetter() throws Exception {
             // define custom getter method
             final Method getter = MyHostObject.class.getMethod("getFoo");
             final Method setter = MyHostObject.class.getMethod("setFoo", Object.class);
-            myHostObject.defineProperty("foo", null, getter, setter, ScriptableObject.EMPTY);
+            myHostObject.defineProperty(
+                    topScope, "foo", null, getter, setter, ScriptableObject.EMPTY);
             topScope.put("MyHostObject", topScope, myHostObject);
 
             final String script =
diff --git a/rhino/src/test/java/org/mozilla/javascript/tests/CustomSetterAcceptNullScriptableTest.java b/rhino/src/test/java/org/mozilla/javascript/tests/CustomSetterAcceptNullScriptableTest.java
index 44d16bf2404..8a5b9c92057 100644
--- a/rhino/src/test/java/org/mozilla/javascript/tests/CustomSetterAcceptNullScriptableTest.java
+++ b/rhino/src/test/java/org/mozilla/javascript/tests/CustomSetterAcceptNullScriptableTest.java
@@ -52,7 +52,8 @@ public void setNullForScriptableSetter() throws Exception {
 
             // define custom setter method
             final Method setMyPropMethod = Foo.class.getMethod("setMyProp", Foo2.class);
-            foo.defineProperty("myProp", null, null, setMyPropMethod, ScriptableObject.EMPTY);
+            foo.defineProperty(
+                    topScope, "myProp", null, null, setMyPropMethod, ScriptableObject.EMPTY);
 
             topScope.put("foo", topScope, foo);
 
diff --git a/rhino/src/test/java/org/mozilla/javascript/tests/DefineFunctionPropertiesTest.java b/rhino/src/test/java/org/mozilla/javascript/tests/DefineFunctionPropertiesTest.java
index f9bda83c156..5cf7bf2a185 100644
--- a/rhino/src/test/java/org/mozilla/javascript/tests/DefineFunctionPropertiesTest.java
+++ b/rhino/src/test/java/org/mozilla/javascript/tests/DefineFunctionPropertiesTest.java
@@ -12,6 +12,7 @@
 import org.mozilla.javascript.Function;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.Undefined;
 
 /**
@@ -21,7 +22,7 @@
  */
 public class DefineFunctionPropertiesTest {
 
-    ScriptableObject global;
+    TopLevel global;
     static Object key = "DefineFunctionPropertiesTest";
 
     /**
@@ -31,10 +32,10 @@ public class DefineFunctionPropertiesTest {
     @Before
     public void setUp() {
         try (Context cx = Context.enter()) {
-            global = cx.initStandardObjects();
+            global = (TopLevel) cx.initStandardObjects();
             String[] names = {"f", "g"};
             global.defineFunctionProperties(
-                    names, DefineFunctionPropertiesTest.class, ScriptableObject.DONTENUM);
+                    global, names, DefineFunctionPropertiesTest.class, ScriptableObject.DONTENUM);
         }
     }
 
@@ -71,7 +72,7 @@ public static Object g(Context cx, Scriptable thisObj, Object[] args, Function f
     @Test
     public void privateData() {
         try (Context cx = Context.enter()) {
-            global.associateValue(key, "bar");
+            global.getGlobalThis().associateValue(key, "bar");
             Object result = cx.evaluateString(global, "g('foo');", "test source", 1, null);
             assertEquals("foobar", result);
         }
diff --git a/rhino/src/test/java/org/mozilla/javascript/tests/DynamicScopeTest.java b/rhino/src/test/java/org/mozilla/javascript/tests/DynamicScopeTest.java
index 0386b77e3c4..81f9aacb11c 100644
--- a/rhino/src/test/java/org/mozilla/javascript/tests/DynamicScopeTest.java
+++ b/rhino/src/test/java/org/mozilla/javascript/tests/DynamicScopeTest.java
@@ -99,7 +99,7 @@ public void standardMethodObjectCreate() {
 
             // Used to fail with org.mozilla.javascript.EvaluatorException: Cannot modify a property
             // of a sealed object: iterator.
-            final ScriptableObject someScope = cx.initStandardObjects();
+            final TopLevel someScope = cx.initStandardObjects();
 
             Scriptable someObj =
                     (Scriptable)
@@ -113,12 +113,12 @@ public void standardMethodObjectCreate() {
                                     "source2",
                                     1,
                                     null);
-            subScope.setParentScope(null);
+            var newTopLevel = TopLevel.createIsolate(someScope, (ScriptableObject) subScope);
 
             Scriptable subObj =
                     (Scriptable)
                             cx.evaluateString(
-                                    subScope,
+                                    newTopLevel,
                                     "var subObj = Object.create(obj); subObj;",
                                     "source3",
                                     1,
diff --git a/rhino/src/test/java/org/mozilla/javascript/tests/IterableTest.java b/rhino/src/test/java/org/mozilla/javascript/tests/IterableTest.java
index c65e3fea5bb..ac87f30c378 100644
--- a/rhino/src/test/java/org/mozilla/javascript/tests/IterableTest.java
+++ b/rhino/src/test/java/org/mozilla/javascript/tests/IterableTest.java
@@ -28,14 +28,14 @@ public class IterableTest {
 
     public static final class FooWithoutSymbols extends FooBoilerplate {
 
-        public FooWithoutSymbols(final Scriptable scope) {
+        public FooWithoutSymbols(TopLevel scope) {
             super(scope);
         }
     }
 
     public static final class FooWithSymbols extends SymbolFooBoilerplate {
 
-        public FooWithSymbols(final Scriptable scope) {
+        public FooWithSymbols(TopLevel scope) {
             super(scope);
         }
 
@@ -47,7 +47,7 @@ public boolean has(Symbol key, Scriptable start) {
 
     public static final class FooWithArrayIterator extends SymbolFooBoilerplate {
 
-        public FooWithArrayIterator(final Scriptable scope) {
+        public FooWithArrayIterator(TopLevel scope) {
             super(scope);
         }
 
@@ -97,7 +97,7 @@ public void forOfUsingNonSymbolScriptable() {
         Utils.runWithAllModes(
                 cx -> {
                     cx.setLanguageVersion(Context.VERSION_ES6);
-                    ScriptableObject scope = cx.initStandardObjects();
+                    TopLevel scope = cx.initStandardObjects();
 
                     Scriptable foo = new FooWithoutSymbols(scope);
                     ScriptableObject.putProperty(scope, "foo", foo);
@@ -131,7 +131,7 @@ public void forOfUsingNonIterable() {
         Utils.runWithAllModes(
                 cx -> {
                     cx.setLanguageVersion(Context.VERSION_ES6);
-                    ScriptableObject scope = cx.initStandardObjects();
+                    TopLevel scope = cx.initStandardObjects();
 
                     Scriptable foo = new FooWithSymbols(scope);
                     ScriptableObject.putProperty(scope, "foo", foo);
@@ -161,7 +161,7 @@ public void forOfUsingArrayIterator() {
         Utils.runWithAllModes(
                 cx -> {
                     cx.setLanguageVersion(Context.VERSION_ES6);
-                    ScriptableObject scope = cx.initStandardObjects();
+                    TopLevel scope = cx.initStandardObjects();
 
                     Scriptable foo = new FooWithArrayIterator(scope);
                     ScriptableObject.putProperty(scope, "foo", foo);
@@ -191,9 +191,9 @@ public void forOfUsingArrayIterator() {
     // Explicitly not a ScriptableObject
     public static class FooBoilerplate implements Scriptable {
 
-        protected final Scriptable scope;
+        protected final TopLevel scope;
 
-        public FooBoilerplate(final Scriptable scope) {
+        public FooBoilerplate(TopLevel scope) {
             this.scope = scope;
         }
 
@@ -283,7 +283,7 @@ public boolean hasInstance(Scriptable instance) {
 
     public static class SymbolFooBoilerplate extends FooBoilerplate implements SymbolScriptable {
 
-        public SymbolFooBoilerplate(final Scriptable scope) {
+        public SymbolFooBoilerplate(TopLevel scope) {
             super(scope);
         }
 
diff --git a/rhino/src/test/java/org/mozilla/javascript/tests/LookupSetterTest.java b/rhino/src/test/java/org/mozilla/javascript/tests/LookupSetterTest.java
index faad37a764e..2dbd2451d9b 100644
--- a/rhino/src/test/java/org/mozilla/javascript/tests/LookupSetterTest.java
+++ b/rhino/src/test/java/org/mozilla/javascript/tests/LookupSetterTest.java
@@ -11,6 +11,7 @@
 import org.mozilla.javascript.ContextAction;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.testutils.Utils;
 
 public class LookupSetterTest {
@@ -149,7 +150,7 @@ public String getClassName() {
         }
     }
 
-    public static class TopScope extends ScriptableObject {
+    public static class TopScope extends TopLevel {
         @Override
         public String getClassName() {
             return "TopScope";
diff --git a/rhino/src/test/java/org/mozilla/javascript/tests/PrimitiveTypeScopeResolutionTest.java b/rhino/src/test/java/org/mozilla/javascript/tests/PrimitiveTypeScopeResolutionTest.java
index ea627ef5ef9..d43e8f44961 100644
--- a/rhino/src/test/java/org/mozilla/javascript/tests/PrimitiveTypeScopeResolutionTest.java
+++ b/rhino/src/test/java/org/mozilla/javascript/tests/PrimitiveTypeScopeResolutionTest.java
@@ -7,6 +7,7 @@
 import org.junit.Test;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.testutils.Utils;
 
 /**
@@ -62,13 +63,14 @@ public void elementAccess() {
     private void testWithTwoScopes(final String scriptScope1, final String scriptScope2) {
         Utils.runWithAllModes(
                 cx -> {
-                    final Scriptable scope1 =
-                            cx.initStandardObjects(new MySimpleScriptableObject("scope1"));
-                    final Scriptable scope2 =
-                            cx.initStandardObjects(new MySimpleScriptableObject("scope2"));
+                    final TopLevel scope1 = new TopLevel(new MySimpleScriptableObject("scope1"));
+                    cx.initStandardObjects(scope1);
+                    final TopLevel scope2 = new TopLevel(new MySimpleScriptableObject("scope2"));
+                    cx.initStandardObjects(scope2);
+
                     cx.evaluateString(scope2, scriptScope2, "source2", 1, null);
 
-                    scope1.put("scope2", scope1, scope2);
+                    scope1.put("scope2", scope1, scope2.getGlobalThis());
 
                     return cx.evaluateString(scope1, scriptScope1, "source1", 1, null);
                 });
@@ -123,17 +125,18 @@ public void functionObjectPrimitiveToObject() throws Exception {
         // define object with custom method
         final MyObject myObject = new MyObject();
         final String[] functionNames = {"readPropFoo"};
-        myObject.defineFunctionProperties(functionNames, MyObject.class, ScriptableObject.EMPTY);
 
         final String scriptScope1 = "String.prototype.foo = 'from 1'; scope2.f()";
 
         Utils.runWithAllModes(
                 cx -> {
-                    final Scriptable scope1 =
-                            cx.initStandardObjects(new MySimpleScriptableObject("scope1"));
-                    final Scriptable scope2 =
-                            cx.initStandardObjects(new MySimpleScriptableObject("scope2"));
+                    final TopLevel scope1 = new TopLevel(new MySimpleScriptableObject("scope1"));
+                    cx.initStandardObjects(scope1);
+                    final TopLevel scope2 = new TopLevel(new MySimpleScriptableObject("scope2"));
+                    cx.initStandardObjects(scope2);
 
+                    myObject.defineFunctionProperties(
+                            scope2, functionNames, MyObject.class, ScriptableObject.EMPTY);
                     scope2.put("myObject", scope2, myObject);
                     cx.evaluateString(scope2, scriptScope2, "source2", 1, null);
 
diff --git a/tests/src/test/java/org/mozilla/javascript/drivers/ScriptTestsBase.java b/tests/src/test/java/org/mozilla/javascript/drivers/ScriptTestsBase.java
index 3fe4666534a..8b0dde4c7ae 100644
--- a/tests/src/test/java/org/mozilla/javascript/drivers/ScriptTestsBase.java
+++ b/tests/src/test/java/org/mozilla/javascript/drivers/ScriptTestsBase.java
@@ -24,6 +24,7 @@
 import org.mozilla.javascript.ScriptRuntime;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.Undefined;
 import org.mozilla.javascript.tools.shell.Global;
 
@@ -71,9 +72,7 @@ private Object executeRhinoScript(boolean interpretedMode) {
             Global global = new Global(cx);
             loadNatives(global);
 
-            Scriptable scope = cx.newObject(global);
-            scope.setPrototype(global);
-            scope.setParentScope(null);
+            var scope = TopLevel.createIsolate(global);
 
             return cx.evaluateReader(scope, script, suiteName, 1, null);
         } catch (JavaScriptException ex) {
diff --git a/tests/src/test/java/org/mozilla/javascript/drivers/ShellTest.java b/tests/src/test/java/org/mozilla/javascript/drivers/ShellTest.java
index 487f06371ec..eec8633de25 100644
--- a/tests/src/test/java/org/mozilla/javascript/drivers/ShellTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/drivers/ShellTest.java
@@ -320,6 +320,7 @@ public static void run(
                                 // invoke after init(...) to make sure ClassCache is available for
                                 // FunctionObject
                                 global.defineFunctionProperties(
+                                        global,
                                         new String[] {"options"},
                                         ShellTest.class,
                                         ScriptableObject.DONTENUM
@@ -429,6 +430,7 @@ public static void runNoFork(
 
             // invoke after init(...) to make sure ClassCache is available for FunctionObject
             global.defineFunctionProperties(
+                    global,
                     new String[] {"options"},
                     ShellTest.class,
                     ScriptableObject.DONTENUM
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/ExternalArrayTest.java b/tests/src/test/java/org/mozilla/javascript/tests/ExternalArrayTest.java
index a17416d2e81..f6fcbba886d 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/ExternalArrayTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/ExternalArrayTest.java
@@ -48,7 +48,7 @@ public void regularArray() {
     public void intArray() {
         ScriptableObject a = (ScriptableObject) cx.newObject(root);
         TestIntArray l = new TestIntArray(10);
-        a.setExternalArrayData(l);
+        a.setExternalArrayData(root, l);
         for (int i = 0; i < 10; i++) {
             l.setArrayElement(i, i);
         }
@@ -63,7 +63,7 @@ public void intArrayThenRemove() {
         ScriptableObject a = (ScriptableObject) cx.newObject(root);
         // Set the external array data
         TestIntArray l = new TestIntArray(10);
-        a.setExternalArrayData(l);
+        a.setExternalArrayData(root, l);
         for (int i = 0; i < 10; i++) {
             l.setArrayElement(i, i);
         }
@@ -76,7 +76,7 @@ public void intArrayThenRemove() {
         // regular JavaScript object.
         a.delete("stringField");
         a.delete("intField");
-        a.setExternalArrayData(null);
+        a.setExternalArrayData(root, null);
         for (int i = 0; i < 10; i++) {
             a.put(i, a, i);
         }
@@ -89,7 +89,7 @@ public void intArrayThenRemove() {
     public void nativeIntArray() {
         ScriptableObject a = (ScriptableObject) cx.newObject(root);
         NativeInt32Array l = new NativeInt32Array(10);
-        a.setExternalArrayData(l);
+        a.setExternalArrayData(root, l);
 
         root.put("testArray", root, a);
         root.put("testArrayLength", root, 10);
@@ -101,7 +101,7 @@ public void nativeIntArray() {
     public void nativeShortArray() {
         ScriptableObject a = (ScriptableObject) cx.newObject(root);
         NativeInt16Array l = new NativeInt16Array(10);
-        a.setExternalArrayData(l);
+        a.setExternalArrayData(root, l);
 
         root.put("testArray", root, a);
         root.put("testArrayLength", root, 10);
@@ -113,7 +113,7 @@ public void nativeShortArray() {
     public void nativeDoubleArray() {
         ScriptableObject a = (ScriptableObject) cx.newObject(root);
         NativeFloat64Array l = new NativeFloat64Array(10);
-        a.setExternalArrayData(l);
+        a.setExternalArrayData(root, l);
 
         root.put("testArray", root, a);
         root.put("testArrayLength", root, 10);
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/ImportClassTest.java b/tests/src/test/java/org/mozilla/javascript/tests/ImportClassTest.java
index e8a938cdbfb..3caa43a22f4 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/ImportClassTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/ImportClassTest.java
@@ -17,8 +17,7 @@
 import org.mozilla.javascript.ImporterTopLevel;
 import org.mozilla.javascript.NativeJavaClass;
 import org.mozilla.javascript.Script;
-import org.mozilla.javascript.Scriptable;
-import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.UniqueTag;
 import org.mozilla.javascript.drivers.TestUtils;
 import org.mozilla.javascript.testutils.Utils;
@@ -80,7 +79,7 @@ public void importInSameContext() {
     public void importMultipleTimes() {
         Utils.runWithAllModes(
                 cx -> {
-                    ScriptableObject sharedScope = cx.initStandardObjects();
+                    TopLevel sharedScope = cx.initStandardObjects();
                     // sharedScope.sealObject(); // code below will try to modify sealed object
 
                     Script script =
@@ -88,10 +87,8 @@ public void importMultipleTimes() {
                                     "importClass(java.util.UUID);true", "TestScript", 1, null);
 
                     for (int i = 0; i < 3; i++) {
-                        Scriptable scope = new ImporterTopLevel(cx);
-                        scope.setPrototype(sharedScope);
-                        scope.setParentScope(null);
-                        script.exec(cx, scope, scope);
+                        var scope = ImporterTopLevel.createIsolate(cx, sharedScope);
+                        script.exec(cx, scope, scope.getGlobalThis());
                         assertEquals(UniqueTag.NOT_FOUND, sharedScope.get("UUID", sharedScope));
                         assertTrue(scope.get("UUID", scope) instanceof NativeJavaClass);
                     }
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/LambdaAccessorSlotTest.java b/tests/src/test/java/org/mozilla/javascript/tests/LambdaAccessorSlotTest.java
index 749fcdcdb2f..fd551651882 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/LambdaAccessorSlotTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/LambdaAccessorSlotTest.java
@@ -127,12 +127,14 @@ public void testRedefineExistingProperty() {
 
                     sh.defineProperty("value", "oldValueOfValue", DONTENUM);
 
-                    sh.defineProperty(cx, "value", (thisObj) -> "valueOfValue", null, DONTENUM);
+                    sh.defineProperty(
+                            cx, scope, "value", (thisObj) -> "valueOfValue", null, DONTENUM);
 
-                    sh.defineProperty(cx, "status", (thisObj) -> 42, null, DONTENUM);
+                    sh.defineProperty(cx, scope, "status", (thisObj) -> 42, null, DONTENUM);
 
                     sh.defineProperty(
                             cx,
+                            scope,
                             "status",
                             (thisObj) -> self(thisObj).getStatus(),
                             (thisObj, value) -> self(thisObj).setStatus(value),
@@ -398,6 +400,7 @@ public void testRedefineExistingProperty_ChangingConfigurableAttr_ShouldFailVali
                                     () ->
                                             sh.defineProperty(
                                                     cx,
+                                                    scope,
                                                     "status",
                                                     (thisObj) -> self(thisObj).getStatus(),
                                                     (thisObj, value) ->
@@ -434,6 +437,7 @@ public void testRedefineExistingProperty_ChangingConfigurableAttr_ShouldFailVali
                                     () ->
                                             sh.defineProperty(
                                                     cx,
+                                                    scope,
                                                     "status",
                                                     (thisObj) -> self(thisObj).getStatus(),
                                                     (thisObj, value) ->
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/NativeWrappedArrayTest.java b/tests/src/test/java/org/mozilla/javascript/tests/NativeWrappedArrayTest.java
index 5c36b8f900d..7589af0ab39 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/NativeWrappedArrayTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/NativeWrappedArrayTest.java
@@ -86,7 +86,7 @@ public void javaArray() throws IOException {
     public void customArray() throws IOException {
         ((ScriptableObject) global)
                 .defineFunctionProperties(
-                        new String[] {"makeCustomArray"}, NativeWrappedArrayTest.class, 0);
+                        global, new String[] {"makeCustomArray"}, NativeWrappedArrayTest.class, 0);
 
         final String setFunc = "function makeTestArray() { return makeCustomArray(); }";
         cx.evaluateString(global, setFunc, "setfunc.js", 1, null);
@@ -108,7 +108,7 @@ public static Object makeCustomArray(
         a.add("two");
         a.add("three");
         a.add("four");
-        return new WrappedArray(thisObj, a);
+        return new WrappedArray(fn.getDeclarationScope(), a);
     }
 
     static class WrappedArray extends ScriptableObject {
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/NestedContextPrototypeTest.java b/tests/src/test/java/org/mozilla/javascript/tests/NestedContextPrototypeTest.java
index cfa775fc26b..fd4aa2cb119 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/NestedContextPrototypeTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/NestedContextPrototypeTest.java
@@ -19,6 +19,7 @@
 import org.mozilla.javascript.ContextFactory;
 import org.mozilla.javascript.EvaluatorException;
 import org.mozilla.javascript.Scriptable;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.tools.shell.Global;
 
 /**
@@ -105,14 +106,13 @@ private Object runScript(String scriptSourceText) {
                                     scope = context.newObject(global);
                                     break;
                                 case SEALED:
-                                    scope = context.newObject(global);
-                                    scope.setPrototype(global);
-                                    scope.setParentScope(null);
+                                    scope = TopLevel.createIsolate(global);
                                     break;
                                 case SEALED_OWN_OBJECTS:
-                                    scope = context.initStandardObjects(null);
-                                    scope.setPrototype(global);
-                                    scope.setParentScope(null);
+                                    scope = context.initStandardObjects(new TopLevel());
+                                    ((TopLevel) scope)
+                                            .getGlobalThis()
+                                            .setPrototype(((TopLevel) global).getGlobalThis());
                                     break;
                                 default:
                                     throw new UnsupportedOperationException();
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/SealedSharedScopeTest.java b/tests/src/test/java/org/mozilla/javascript/tests/SealedSharedScopeTest.java
index b2979157586..dbe44b2faef 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/SealedSharedScopeTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/SealedSharedScopeTest.java
@@ -22,6 +22,7 @@
 import org.mozilla.javascript.ImporterTopLevel;
 import org.mozilla.javascript.JSFunction;
 import org.mozilla.javascript.Scriptable;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.Wrapper;
 
 @RunWith(BlockJUnit4ClassRunner.class)
@@ -41,12 +42,8 @@ public void setUp() throws Exception {
 
         ctx = Context.enter();
         ctx.setLanguageVersion(Context.VERSION_DEFAULT);
-        scope1 = ctx.newObject(sharedScope);
-        scope1.setPrototype(sharedScope);
-        scope1.setParentScope(null);
-        scope2 = ctx.newObject(sharedScope);
-        scope2.setPrototype(sharedScope);
-        scope2.setParentScope(null);
+        scope1 = TopLevel.createIsolate(sharedScope);
+        scope2 = TopLevel.createIsolate(sharedScope);
     }
 
     @After
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/StrictModeApiTest.java b/tests/src/test/java/org/mozilla/javascript/tests/StrictModeApiTest.java
index 0bec3fd7d04..193d01da757 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/StrictModeApiTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/StrictModeApiTest.java
@@ -49,7 +49,12 @@ public void onlyGetterError() {
                         ScriptableObject.defineClass(scope, MyHostObject.class);
                         final Method readMethod = MyHostObject.class.getMethod("jsxGet_x");
                         prototype.defineProperty(
-                                "readonlyProp", null, readMethod, null, ScriptableObject.EMPTY);
+                                scope,
+                                "readonlyProp",
+                                null,
+                                readMethod,
+                                null,
+                                ScriptableObject.EMPTY);
 
                         ScriptableObject.defineProperty(
                                 scope, "o", prototype, ScriptableObject.DONTENUM);
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/Test262SuiteTest.java b/tests/src/test/java/org/mozilla/javascript/tests/Test262SuiteTest.java
index 25a75e7151a..c6bea8c2d0c 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/Test262SuiteTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/Test262SuiteTest.java
@@ -223,8 +223,8 @@ public static class $262 extends ScriptableObject {
             proto.defineProperty(scope, "evalScript", 1, $262::evalScript);
             proto.defineProperty(scope, "detachArrayBuffer", 0, $262::detachArrayBuffer);
 
-            proto.defineProperty(cx, "global", $262::getGlobal, null, DONTENUM | READONLY);
-            proto.defineProperty(cx, "agent", $262::getAgent, null, DONTENUM | READONLY);
+            proto.defineProperty(cx, scope, "global", $262::getGlobal, null, DONTENUM | READONLY);
+            proto.defineProperty(cx, scope, "agent", $262::getAgent, null, DONTENUM | READONLY);
 
             proto.defineProperty(SymbolKey.TO_STRING_TAG, "__262__", DONTENUM | READONLY);
 
@@ -256,7 +256,7 @@ public static Object evalScript(
         }
 
         public static Object getGlobal(Scriptable scriptable) {
-            return scriptable.getParentScope();
+            return ((TopLevel) scriptable.getParentScope()).getGlobalThis();
         }
 
         public static $262 createRealm(
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/WriteReadOnlyPropertyTest.java b/tests/src/test/java/org/mozilla/javascript/tests/WriteReadOnlyPropertyTest.java
index 366765c14c1..35fdfb7fd58 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/WriteReadOnlyPropertyTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/WriteReadOnlyPropertyTest.java
@@ -49,8 +49,6 @@ public void writeReadOnly_throws() throws Exception {
 
     void testWriteReadOnly(final boolean acceptWriteReadOnly) throws Exception {
         final Method readMethod = Foo.class.getMethod("getMyProp", (Class[]) null);
-        final Foo foo = new Foo("hello");
-        foo.defineProperty("myProp", null, readMethod, null, ScriptableObject.EMPTY);
 
         final String script = "foo.myProp = 123; foo.myProp";
 
@@ -67,6 +65,9 @@ protected boolean hasFeature(final Context cx, final int featureIndex) {
         contextFactory.call(
                 cx -> {
                     final ScriptableObject top = cx.initStandardObjects();
+                    final Foo foo = new Foo("hello");
+                    foo.defineProperty(
+                            top, "myProp", null, readMethod, null, ScriptableObject.EMPTY);
                     ScriptableObject.putProperty(top, "foo", foo);
 
                     cx.evaluateString(top, script, "script", 0, null);
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/commonjs/module/ComplianceTest.java b/tests/src/test/java/org/mozilla/javascript/tests/commonjs/module/ComplianceTest.java
index ecd86373675..cbbcb718ff4 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/commonjs/module/ComplianceTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/commonjs/module/ComplianceTest.java
@@ -17,6 +17,7 @@
 import org.mozilla.javascript.Function;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.commonjs.module.Require;
 import org.mozilla.javascript.commonjs.module.provider.StrongCachingModuleScriptProvider;
 import org.mozilla.javascript.commonjs.module.provider.UrlModuleSourceProvider;
@@ -45,7 +46,7 @@ public static Collection<Object[]> data() {
         return retval;
     }
 
-    private static Require createRequire(File dir, Context cx, Scriptable scope)
+    private static Require createRequire(File dir, Context cx, TopLevel scope)
             throws URISyntaxException {
         return new Require(
                 cx,
@@ -68,7 +69,7 @@ private static Require createRequire(File dir, Context cx, Scriptable scope)
     public void require() throws Throwable {
         Utils.runWithAllModes(
                 cx -> {
-                    final Scriptable scope = cx.initStandardObjects();
+                    final TopLevel scope = cx.initStandardObjects();
                     ScriptableObject.putProperty(scope, "print", new Print(scope));
                     try {
                         createRequire(testDir, cx, scope).requireMain(cx, "program");
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/commonjs/module/RequireTest.java b/tests/src/test/java/org/mozilla/javascript/tests/commonjs/module/RequireTest.java
index 1d961183ba0..9fd8b1f738d 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/commonjs/module/RequireTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/commonjs/module/RequireTest.java
@@ -16,6 +16,7 @@
 import org.mozilla.javascript.ScriptStackElement;
 import org.mozilla.javascript.Scriptable;
 import org.mozilla.javascript.ScriptableObject;
+import org.mozilla.javascript.TopLevel;
 import org.mozilla.javascript.commonjs.module.Require;
 import org.mozilla.javascript.commonjs.module.provider.StrongCachingModuleScriptProvider;
 import org.mozilla.javascript.commonjs.module.provider.UrlModuleSourceProvider;
@@ -75,13 +76,13 @@ public String getClassName() {
     @Test
     public void customGlobal() throws Exception {
         try (Context cx = createContext()) {
-            final Scriptable scope = cx.initStandardObjects();
+            final TopLevel scope = cx.initStandardObjects();
             ScriptableObject.defineClass(scope, CustomGlobal.class);
 
-            final Scriptable global = cx.newObject(scope, "CustomGlobal", null);
-
-            global.getPrototype().setPrototype(scope);
-            global.setParentScope(null);
+            var obj = cx.newObject(scope, "CustomGlobal", null);
+            obj.getPrototype().setPrototype(scope.getGlobalThis());
+            final TopLevel global =
+                    TopLevel.createIsolateCustomPrototypeChain(scope, (ScriptableObject) obj);
 
             final Require require =
                     new Require(
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/es6/FunctionNullSetTest.java b/tests/src/test/java/org/mozilla/javascript/tests/es6/FunctionNullSetTest.java
index 6ac3447ad48..8ae9c9d8c57 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/es6/FunctionNullSetTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/es6/FunctionNullSetTest.java
@@ -38,6 +38,7 @@ public Object run(final Context cx) {
                             final Method setterMethod =
                                     MyHostObject.class.getMethod("jsxSet_onclick", Object.class);
                             prototype.defineProperty(
+                                    scope,
                                     "onclick",
                                     null,
                                     getterMethod,
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/es6/ParentPropertyTest.java b/tests/src/test/java/org/mozilla/javascript/tests/es6/ParentPropertyTest.java
index 77ed228a90f..97123d3ce76 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/es6/ParentPropertyTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/es6/ParentPropertyTest.java
@@ -18,7 +18,7 @@ public void parentGet() {
         // https://whereswalden.com/2010/05/07/spidermonkey-change-du-jour-the-special-__parent__-property-has-been-removed/
         String script = "var a = {};" + "'' + a.__parent__;";
 
-        Utils.assertWithAllModes_1_8("[object Object]", script);
+        Utils.assertWithAllModes_1_8("[object topLevel]", script);
         Utils.assertWithAllModes_ES6("undefined", script);
     }
 }
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/es6/PropertyTest.java b/tests/src/test/java/org/mozilla/javascript/tests/es6/PropertyTest.java
index da233cb8470..e29ed61d9f1 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/es6/PropertyTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/es6/PropertyTest.java
@@ -33,7 +33,7 @@ public void prototypeProperty() throws Exception {
                         final Method getter = MyHostObject.class.getMethod("getFoo");
                         final Method setter = MyHostObject.class.getMethod("setFoo", String.class);
                         myHostObject.defineProperty(
-                                "foo", null, getter, setter, ScriptableObject.EMPTY);
+                                scope, "foo", null, getter, setter, ScriptableObject.EMPTY);
                         scope.put("MyHostObject", scope, myHostObject);
                     } catch (Exception e) {
                     }
@@ -70,7 +70,7 @@ public void redefineGetterProperty() throws Exception {
                         final Method getter = MyHostObject.class.getMethod("getFoo");
                         final Method setter = MyHostObject.class.getMethod("setFoo", String.class);
                         myHostObject.defineProperty(
-                                "foo", null, getter, setter, ScriptableObject.EMPTY);
+                                scope, "foo", null, getter, setter, ScriptableObject.EMPTY);
                         scope.put("MyHostObject", scope, myHostObject);
                     } catch (Exception e) {
                     }
@@ -107,7 +107,7 @@ public void redefineSetterProperty() throws Exception {
                         Method getter = MyHostObject.class.getMethod("getFoo");
                         final Method setter = MyHostObject.class.getMethod("setFoo", String.class);
                         myHostObject.defineProperty(
-                                "foo", null, getter, setter, ScriptableObject.EMPTY);
+                                scope, "foo", null, getter, setter, ScriptableObject.EMPTY);
                         scope.put("MyHostObject", scope, myHostObject);
                     } catch (Exception e) {
                     }
@@ -146,7 +146,8 @@ public void redefinePropertyWithThreadSafeSlotMap() {
                 // define custom getter method
                 final Method getter = MyHostObject.class.getMethod("getFoo");
                 final Method setter = MyHostObject.class.getMethod("setFoo", String.class);
-                myHostObject.defineProperty("foo", null, getter, setter, ScriptableObject.EMPTY);
+                myHostObject.defineProperty(
+                        scope, "foo", null, getter, setter, ScriptableObject.EMPTY);
                 scope.put("MyHostObject", scope, myHostObject);
             } catch (Exception e) {
             }
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/type_info/CustomTypeInfoFactoryTest.java b/tests/src/test/java/org/mozilla/javascript/tests/type_info/CustomTypeInfoFactoryTest.java
index 43ba811b639..c31dc2ceb2e 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/type_info/CustomTypeInfoFactoryTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/type_info/CustomTypeInfoFactoryTest.java
@@ -31,7 +31,7 @@ public void associate() throws Exception {
         var contextFactory = new ContextFactory();
 
         try (var cx = contextFactory.enterContext()) {
-            var scope = new NativeObject();
+            var scope = new TopLevel();
             new NoGenericNoCacheFactory().associate(scope);
             cx.initStandardObjects(scope);
 
@@ -59,7 +59,7 @@ public void serdeCustom() throws Exception {
         var contextFactory = new ContextFactory();
         byte[] data;
         try (var cx = contextFactory.enterContext()) {
-            var scope = new NativeObject();
+            var scope = new TopLevel();
             new NoGenericNoCacheFactory().associate(scope);
             cx.initStandardObjects(scope);
 
@@ -79,7 +79,7 @@ public void serdeGlobal() throws Exception {
         var contextFactory = new ContextFactory();
         byte[] data;
         try (var cx = contextFactory.enterContext()) {
-            var scope = new NativeObject();
+            var scope = new TopLevel();
             TypeInfoFactory.GLOBAL.associate(scope);
             cx.initStandardObjects(scope);
 
diff --git a/tests/testsrc/doctests/xmlOptions.doctest b/tests/testsrc/doctests/xmlOptions.doctest
index bed5a3b5c62..bc9ce116e2c 100644
--- a/tests/testsrc/doctests/xmlOptions.doctest
+++ b/tests/testsrc/doctests/xmlOptions.doctest
@@ -9,11 +9,11 @@ js> x
     <baz>1</baz>
   </bar>
 </foo>
-js> var xmlLib = org.mozilla.javascript.xml.XMLLib.extractFromScope(this);
+js> var xmlLib = __xml_lib__;
 js> xmlLib.isPrettyPrinting();
 true
 js> xmlLib.setPrettyPrinting(false);
 js> xmlLib.isPrettyPrinting();
 false
 js> x
-<foo><bar><baz>1</baz></bar></foo>
\ No newline at end of file
+<foo><bar><baz>1</baz></bar></foo>