diff --git a/platform/lang-impl/src/com/intellij/psi/stubs/StubUpdatingIndex.java b/platform/lang-impl/src/com/intellij/psi/stubs/StubUpdatingIndex.java
index f822365e4e64..57997b4245a0 100644
--- a/platform/lang-impl/src/com/intellij/psi/stubs/StubUpdatingIndex.java
+++ b/platform/lang-impl/src/com/intellij/psi/stubs/StubUpdatingIndex.java
@@ -33,7 +33,6 @@ import com.intellij.openapi.vfs.newvfs.NewVirtualFile;
 import com.intellij.openapi.vfs.newvfs.persistent.FSRecords;
 import com.intellij.psi.tree.IFileElementType;
 import com.intellij.psi.tree.IStubFileElementType;
-import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.indexing.*;
 import com.intellij.util.indexing.impl.*;
 import com.intellij.util.io.*;
@@ -107,11 +106,6 @@ public class StubUpdatingIndex extends SingleEntryFileBasedIndexExtension<Serial
     return 5; // no need to cache many serialized trees
   }
 
-  @Override
-  public boolean keyIsUniqueForIndexedFile() {
-    return true;
-  }
-
   @NotNull
   @Override
   public SingleEntryIndexer<SerializedStubTree> getIndexer() {