Index: src/java/org/apache/lucene/index/IndexReader.java
===================================================================
--- src/java/org/apache/lucene/index/IndexReader.java	(revision 788015)
+++ src/java/org/apache/lucene/index/IndexReader.java	(working copy)
@@ -114,7 +114,8 @@
   protected boolean hasChanges;
   
   private volatile int refCount;
-
+  private boolean isOpen;
+  
   private boolean disableFakeNorms = false;
 
   /** Expert: returns the current refCount for this reader */
@@ -140,6 +141,7 @@
     assert refCount > 0;
     ensureOpen();
     refCount++;
+    isOpen = true;
   }
 
   /**
@@ -158,6 +160,10 @@
     if (refCount == 1) {
       commit();
       doClose();
+      isOpen = false;
+      // preventing re-calling this method if decRef() followed by a close()
+      // happens.
+      closed = true;
     }
     refCount--;
   }
@@ -189,13 +195,14 @@
   
   protected IndexReader() { 
     refCount = 1;
+    isOpen = true;
   }
   
   /**
    * @throws AlreadyClosedException if this IndexReader is closed
    */
   protected final void ensureOpen() throws AlreadyClosedException {
-    if (refCount <= 0) {
+    if (!isOpen) {
       throw new AlreadyClosedException("this IndexReader is closed");
     }
   }