Index: lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java
===================================================================
--- lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java	(revision 1392824)
+++ lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java	(working copy)
@@ -577,8 +577,8 @@
         if (assertNoUnreferencedFilesOnClose) {
           // now look for unreferenced files:
           String[] startFiles = listAll();
-          new IndexWriter(this, new IndexWriterConfig(LuceneTestCase.TEST_VERSION_CURRENT, null)).rollback();
-          String[] endFiles = listAll();
+          new IndexWriter(delegate, new IndexWriterConfig(LuceneTestCase.TEST_VERSION_CURRENT, null)).rollback();
+          String[] endFiles = delegate.listAll();
 
           Arrays.sort(startFiles);
           Arrays.sort(endFiles);