diff --git a/core/src/main/java/jenkins/scm/RunWithSCM.java b/core/src/main/java/jenkins/scm/RunWithSCM.java
index 5c784b175f36..f6a04aa5bd1f 100644
--- a/core/src/main/java/jenkins/scm/RunWithSCM.java
+++ b/core/src/main/java/jenkins/scm/RunWithSCM.java
@@ -34,6 +34,7 @@
 import hudson.scm.SCM;
 import hudson.util.AdaptedIterator;
 import java.util.AbstractSet;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
@@ -93,8 +94,12 @@ public interface RunWithSCM<JobT extends Job<JobT, RunT>,
             return calculateCulprits();
         }
 
+        Set<String> ids = getCulpritIds();
+
         return new AbstractSet<>() {
-            private Set<String> culpritIds = Set.copyOf(getCulpritIds());
+
+            private final Set<String> culpritIds = (ids == null)
+                    ? Collections.emptySet() : Collections.unmodifiableSet(new HashSet<>(ids));
 
             @Override
             public Iterator<User> iterator() {
diff --git a/core/src/test/java/jenkins/scm/RunWithSCMTest.java b/core/src/test/java/jenkins/scm/RunWithSCMTest.java
new file mode 100644
index 000000000000..d44bd2f835e5
--- /dev/null
+++ b/core/src/test/java/jenkins/scm/RunWithSCMTest.java
@@ -0,0 +1,92 @@
+package jenkins.scm;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import hudson.model.User;
+import hudson.scm.ChangeLogSet;
+import java.util.AbstractSet;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+import org.jspecify.annotations.NonNull;
+import org.junit.jupiter.api.Test;
+
+class RunWithSCMTest {
+
+    /**
+     * Regression test for corrupted UnmodifiableCollection
+     * Set.copyOf() throws NPE
+     * This was a regression introduced when migrating from Collections.unmodifiableSet to Set.copyOf.
+     */
+    @Test
+    void getCulprits_shouldHandleCorruptedCollectionThatThrowsNPE() {
+        RunWithSCM run = new RunWithSCM() {
+            @Override
+            public boolean shouldCalculateCulprits() {
+                return false;
+            }
+
+            @Override
+            public @NonNull List<ChangeLogSet<? extends ChangeLogSet.Entry>> getChangeSets() {
+                return List.of();
+            }
+
+            @Override
+            public Set<String> getCulpritIds() {
+                // Simulates corrupted UnmodifiableCollection
+                return new AbstractSet<>() {
+                    @Override
+                    public Iterator<String> iterator() {
+                        return Collections.emptyIterator();
+                    }
+
+                    @Override
+                    public int size() {
+                        return 0;
+                    }
+
+                    @Override
+                    public boolean isEmpty() {
+                        throw new NullPointerException("c is null");
+                    }
+                };
+            }
+        };
+
+        // Should not throw NPE, should return empty set
+        Set<User> culprits = run.getCulprits();
+
+        assertNotNull(culprits);
+        assertEquals(0, culprits.size());
+    }
+
+    /**
+     * Tests that null return from getCulpritIds() is handled gracefully.
+     */
+    @Test
+    void getCulprits_shouldHandleNullCulpritIds() {
+        RunWithSCM run = new RunWithSCM() {
+            @Override
+            public boolean shouldCalculateCulprits() {
+                return false;
+            }
+
+            @Override
+            public @NonNull List<ChangeLogSet<? extends ChangeLogSet.Entry>> getChangeSets() {
+                return List.of();
+            }
+
+            @Override
+            public Set<String> getCulpritIds() {
+                return null;
+            }
+        };
+
+        Set<User> culprits = run.getCulprits();
+
+        assertNotNull(culprits);
+        assertEquals(0, culprits.size());
+    }
+}