Index: src/java/org/apache/lucene/index/DirectoryReader.java
===================================================================
--- src/java/org/apache/lucene/index/DirectoryReader.java	(revision 1042635)
+++ src/java/org/apache/lucene/index/DirectoryReader.java	(working copy)
@@ -548,7 +548,9 @@
   @Override
   public boolean isOptimized() {
     ensureOpen();
-    return segmentInfos.size() == 1 && !hasDeletions();
+    final SegmentInfos infos = segmentInfosStart != null ? segmentInfosStart
+        : segmentInfos;
+    return infos.size() == 1 && !hasDeletions();
   }
 
   @Override