Index: lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java
===================================================================
--- lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java	(revision 1392825)
+++ lucene/test-framework/src/java/org/apache/lucene/store/MockDirectoryWrapper.java	(working copy)
@@ -204,10 +204,11 @@
     // first force-close all files, so we can corrupt on windows etc.
     // clone the file map, as these guys want to remove themselves on close.
     Map<Closeable,Exception> m = new IdentityHashMap<Closeable,Exception>(openFileHandles);
-    for (Closeable f : m.keySet())
+    for (Closeable f : m.keySet()) {
       try {
         f.close();
       } catch (Exception ignored) {}
+    }
     
     while(it.hasNext()) {
       String name = it.next();
@@ -577,8 +578,8 @@
         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);
Index: lucene/core/src/java/org/apache/lucene/index/SegmentInfoPerCommit.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/SegmentInfoPerCommit.java	(revision 1392825)
+++ lucene/core/src/java/org/apache/lucene/index/SegmentInfoPerCommit.java	(working copy)
@@ -79,6 +79,7 @@
 
   /** Returns all files in use by this segment. */
   public Collection<String> files() throws IOException {
+    // Start from the wrapped info's files:
     Collection<String> files = new HashSet<String>(info.files());
 
     // Must separately add any live docs files:
Index: lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/IndexWriter.java	(revision 1392825)
+++ lucene/core/src/java/org/apache/lucene/index/IndexWriter.java	(working copy)
@@ -3136,6 +3136,11 @@
       }
     }
 
+    if (dropSegment) {
+      assert !segmentInfos.contains(merge.info);
+      deleter.deleteNewFiles(merge.info.files());
+    }
+
     // Must close before checkpoint, otherwise IFD won't be
     // able to delete the held-open files from the merge
     // readers:
Index: lucene/core/src/test/org/apache/lucene/index/TestRollingUpdates.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/index/TestRollingUpdates.java	(revision 1392825)
+++ lucene/core/src/test/org/apache/lucene/index/TestRollingUpdates.java	(working copy)
@@ -39,7 +39,6 @@
   public void testRollingUpdates() throws Exception {
     Random random = new Random(random().nextLong());
     final BaseDirectoryWrapper dir = newDirectory();
-    dir.setCheckIndexOnClose(false); // we use a custom codec provider
     final LineFileDocs docs = new LineFileDocs(random, true);
 
     //provider.register(new MemoryCodec());
@@ -130,10 +129,11 @@
     assertEquals(SIZE, w.numDocs());
 
     w.close();
+
+    TestIndexWriter.assertNoUnreferencedFiles(dir, "leftover files after rolling updates");
+
     docs.close();
     
-    _TestUtil.checkIndex(dir);
-
     // LUCENE-4455:
     SegmentInfos infos = new SegmentInfos();
     infos.read(dir);