Index: CHANGES.txt
===================================================================
--- CHANGES.txt	(revision 826548)
+++ CHANGES.txt	(working copy)
@@ -107,6 +107,9 @@
 * LUCENE-1986: Fix NPE when scoring PayloadNearQuery (Peter Keegan,
   Mark Miller via Mike McCandless)
 
+* LUCENE-1992: Fix thread hazard if a merge is committing just as an
+  exception occurs during sync (Uwe Schindler, Mike McCandless)
+
 New features
 
 * LUCENE-1933: Provide a convenience AttributeFactory that creates a
Index: src/test/org/apache/lucene/index/TestIndexWriter.java
===================================================================
--- src/test/org/apache/lucene/index/TestIndexWriter.java	(revision 826548)
+++ src/test/org/apache/lucene/index/TestIndexWriter.java	(working copy)
@@ -2698,8 +2698,6 @@
     failure.setDoFail();
 
     ConcurrentMergeScheduler cms = new ConcurrentMergeScheduler();
-    // We expect sync exceptions in the merge threads
-    cms.setSuppressExceptions();
     writer.setMergeScheduler(cms);
     writer.setMaxBufferedDocs(2);
     writer.setMergeFactor(5);
Index: src/java/org/apache/lucene/index/IndexWriter.java
===================================================================
--- src/java/org/apache/lucene/index/IndexWriter.java	(revision 826548)
+++ src/java/org/apache/lucene/index/IndexWriter.java	(working copy)
@@ -3812,7 +3812,7 @@
 
     // Must note the change to segmentInfos so any commits
     // in-flight don't lose it:
-    changeCount++;
+    checkpoint();
 
     // If the merged segments had pending changes, clear
     // them so that they don't bother writing them to