Index: src/test/org/apache/lucene/index/TestIndexReaderClone.java
===================================================================
--- src/test/org/apache/lucene/index/TestIndexReaderClone.java	(revision 741907)
+++ src/test/org/apache/lucene/index/TestIndexReaderClone.java	(working copy)
@@ -403,4 +403,24 @@
   private void assertDelDocsRefCountEquals(int refCount, SegmentReader reader) {
     assertEquals(refCount, reader.deletedDocsRef.refCount());
   }
+  
+  public void testCloneSubreaders() throws Exception {
+    final Directory dir1 = new MockRAMDirectory();
+ 
+    TestIndexReaderReopen.createIndex(dir1, true);
+    IndexReader reader = IndexReader.open(dir1);
+    reader.deleteDocument(1); // acquire write lock
+    IndexReader[] subs = reader.getSequentialSubReaders();
+    assert subs.length > 1;
+    
+    IndexReader[] clones = new IndexReader[subs.length];
+    for (int x=0; x < subs.length; x++) {
+      clones[x] = (IndexReader) subs[x].clone();
+    }
+    reader.close();
+    for (int x=0; x < subs.length; x++) {
+      clones[x].close();
+    }
+    dir1.close();
+  }
 }
Index: src/java/org/apache/lucene/index/DirectoryIndexReader.java
===================================================================
--- src/java/org/apache/lucene/index/DirectoryIndexReader.java	(revision 741907)
+++ src/java/org/apache/lucene/index/DirectoryIndexReader.java	(working copy)
@@ -167,11 +167,16 @@
   
   public final synchronized IndexReader clone(boolean openReadOnly) throws CorruptIndexException, IOException {
 
-    final SegmentInfos infos = (SegmentInfos) segmentInfos.clone();
-    DirectoryIndexReader newReader = doReopen(infos, true, openReadOnly);
+    final SegmentInfos clonedInfos;
+    if (segmentInfos != null) {
+      clonedInfos = (SegmentInfos) segmentInfos.clone();
+    } else {
+      clonedInfos = null;
+    }
+    DirectoryIndexReader newReader = doReopen(clonedInfos, true, openReadOnly);
     
     if (this != newReader) {
-      newReader.init(directory, infos, closeDirectory, openReadOnly);
+      newReader.init(directory, clonedInfos, closeDirectory, openReadOnly);
       newReader.deletionPolicy = deletionPolicy;
     }
 
Index: src/java/org/apache/lucene/index/SegmentReader.java
===================================================================
--- src/java/org/apache/lucene/index/SegmentReader.java	(revision 741907)
+++ src/java/org/apache/lucene/index/SegmentReader.java	(working copy)
@@ -625,8 +625,15 @@
 
   protected synchronized DirectoryIndexReader doReopen(SegmentInfos infos, boolean doClone, boolean openReadOnly) throws CorruptIndexException, IOException {
     DirectoryIndexReader newReader;
-    
-    if (infos.size() == 1) {
+
+    if (infos == null) {
+      if (doClone) {
+        // OK: directly clone myself
+        newReader = reopenSegment(si, doClone, openReadOnly);
+      } else {
+        throw new UnsupportedOperationException("cannot reopen a standalone SegmentReader");
+      }
+    } else if (infos.size() == 1) {
       SegmentInfo si = infos.info(0);
       if (segment.equals(si.name) && si.getUseCompoundFile() == SegmentReader.this.si.getUseCompoundFile()) {
         newReader = reopenSegment(si, doClone, openReadOnly);