Index: src/test/org/apache/lucene/index/TestIndexWriter.java
===================================================================
--- src/test/org/apache/lucene/index/TestIndexWriter.java	(revision 885071)
+++ src/test/org/apache/lucene/index/TestIndexWriter.java	(working copy)
@@ -4610,4 +4610,46 @@
     _TestUtil.checkIndex(dir);
     dir.close();
   }
+
+  public void testNRTDiskUsageAfterOptimize() throws Exception {
+    Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_CURRENT);
+
+    for(int i=0;i<4;i++) {
+      boolean doNRT = (i&1) != 0;
+      boolean doCFS = i < 2;
+
+      MockRAMDirectory dir = new MockRAMDirectory();
+      IndexWriter writer = new IndexWriter(dir, analyzer, true, IndexWriter.MaxFieldLength.UNLIMITED);
+      writer.setUseCompoundFile(doCFS);
+      writer.setMaxBufferedDocs(444);
+      Document doc = new Document();
+      Field f = new Field("foo", "", Field.Store.YES, Field.Index.NOT_ANALYZED);
+      doc.add(f);
+      for(int j = 0; j < 10000; j++) {
+        f.setValue("bar " + j);
+        writer.addDocument(doc);
+      }
+
+      writer.commit();
+
+      final long sz = dir.getRecomputedActualSizeInBytes();
+      IndexReader r;
+      if (doNRT) {
+        r = writer.getReader();
+      } else {
+        r = IndexReader.open(dir);
+      }
+
+      writer.optimize();
+      r.close();
+      // should force files to be reclaimed:
+      writer.commit();
+      
+      final long sz2 = dir.getRecomputedActualSizeInBytes();
+      assertTrue("start size=" + (sz/1024./1024.) + "; end size=" + (sz2/1024./1024.) + " doNRT=" + doNRT + " doCFS=" + doCFS, sz2 <= sz);
+      
+      writer.close();
+      dir.close();
+    }
+  }
 }