diff --git a/platform/core-impl/src/com/intellij/openapi/vfs/impl/VirtualFilePointerContainerImpl.java b/platform/core-impl/src/com/intellij/openapi/vfs/impl/VirtualFilePointerContainerImpl.java
index 5702cf351133..d972b22044df 100644
--- a/platform/core-impl/src/com/intellij/openapi/vfs/impl/VirtualFilePointerContainerImpl.java
+++ b/platform/core-impl/src/com/intellij/openapi/vfs/impl/VirtualFilePointerContainerImpl.java
@@ -405,8 +405,8 @@ public class VirtualFilePointerContainerImpl extends TraceableDisposable impleme
       if (!jars.contains(pointer)) toAddJars.add(pointer);
       if (!list.contains(pointer)) toAddList.add(pointer);
     });
-    (recursively ? myJarRecursiveDirectories : myJarDirectories).addAll(toAddJars);
-    myList.addAll(toAddList); // hack. jar directories need to be contained in class roots too (for externalization compatibility) but be ignored in getFiles()
+    (recursively ? myJarRecursiveDirectories : myJarDirectories).addAllAbsent(toAddJars);
+    myList.addAllAbsent(toAddList); // hack. jar directories need to be contained in class roots too (for externalization compatibility) but be ignored in getFiles()
     dropCaches();
   }