diff --git a/smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/traits/EndpointTestsTraitValidator.java b/smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/traits/EndpointTestsTraitValidator.java
index 1761769ee81..bb13da282ca 100644
--- a/smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/traits/EndpointTestsTraitValidator.java
+++ b/smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/traits/EndpointTestsTraitValidator.java
@@ -61,13 +61,14 @@ public List<ValidationEvent> validate(Model model) {
                                 testOperationInput);
 
                         // Error test cases may use invalid inputs as the mechanism to trigger their error,
-                        // so lower the severity before emitting.
-                        if (testCase.getExpect().getError().isPresent()) {
-                            for (ValidationEvent event : operationInputEvents) {
-                                events.add(event.toBuilder().severity(Severity.WARNING).build());
+                        // so lower the severity before emitting. All other events here should be raised to
+                        // DANGER level as well.
+                        for (ValidationEvent event : operationInputEvents) {
+                            if (event.getSeverity() == Severity.WARNING
+                                    || event.getSeverity() == Severity.NOTE
+                                    || testCase.getExpect().getError().isPresent()) {
+                                events.add(event.toBuilder().severity(Severity.DANGER).build());
                             }
-                        } else {
-                            events.addAll(operationInputEvents);
                         }
                     }
                 }
diff --git a/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-input-target.errors b/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-input-target.errors
new file mode 100644
index 00000000000..f9e9d70d1a4
--- /dev/null
+++ b/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-input-target.errors
@@ -0,0 +1,2 @@
+[WARNING] smithy.example#InvalidService: This shape applies a trait that is unstable: smithy.rules#endpointTests | UnstableTrait
+[DANGER] smithy.example#InvalidService: The operationInput value for an endpoint test does not match the operation's input shape: Invalid structure member `fizz` found for `smithy.example#GetThingInput` | EndpointTestsTrait.smithy.example#GetThingInput.fizz
diff --git a/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-input-target.smithy b/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-input-target.smithy
new file mode 100644
index 00000000000..6e12707603d
--- /dev/null
+++ b/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-input-target.smithy
@@ -0,0 +1,45 @@
+$version: "2.0"
+
+namespace smithy.example
+
+use smithy.rules#endpointTests
+
+service InvalidService {
+    version: "2022-01-01"
+    operations: [
+        GetThing
+    ]
+}
+
+apply InvalidService @endpointTests({
+    version: "1.0"
+    testCases: [
+        {
+            params: { stringFoo: "c d", boolFoo: true }
+            operationInputs: [
+                {
+                    operationName: "GetThing"
+                    operationParams: { fizz: "something", buzz: "a buzz value" }
+                }
+            ]
+            expect: {
+                endpoint: {
+                    url: "https://example.com"
+                    properties: {}
+                    headers: {
+                        single: ["foo"]
+                        multi: ["foo", "bar", "baz"]
+                    }
+                }
+            }
+        }
+    ]
+})
+
+@readonly
+operation GetThing {
+    input := {
+        buzz: String
+        fuzz: String
+    }
+}
diff --git a/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-required-values.errors b/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-required-values.errors
index 687a07963e4..dbcbbfdc7f1 100644
--- a/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-required-values.errors
+++ b/smithy-rules-engine/src/test/resources/software/amazon/smithy/rulesengine/traits/errorfiles/missing-required-values.errors
@@ -1,2 +1,2 @@
 [WARNING] smithy.example#InvalidService: This shape applies a trait that is unstable: smithy.rules#endpointTests | UnstableTrait
-[WARNING] smithy.example#InvalidService: The operationInput value for an endpoint test does not match the operation's input shape: Missing required structure member `fizz` for `smithy.example#GetThingInput` | EndpointTestsTrait
+[DANGER] smithy.example#InvalidService: The operationInput value for an endpoint test does not match the operation's input shape: Missing required structure member `fizz` for `smithy.example#GetThingInput` | EndpointTestsTrait