diff --git a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/model/CModelManager.java b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/model/CModelManager.java
index 076b6bd8ed8..4498b1576cb 100644
--- a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/model/CModelManager.java
+++ b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/model/CModelManager.java
@@ -1374,7 +1374,7 @@ public class CModelManager implements IResourceChangeListener, IContentTypeChang
 			perFactoryWorkingCopies = new HashMap<ITranslationUnit, WorkingCopy>();
 			sharedWorkingCopies.put(factory, perFactoryWorkingCopies);
 		}
-		WorkingCopy workingCopy = perFactoryWorkingCopies.get(this);
+		WorkingCopy workingCopy = perFactoryWorkingCopies.get(tu);
 		if (workingCopy != null) {
 			workingCopy.useCount++;
 			return workingCopy;