Index: src/main/java/org/apache/jackrabbit/core/query/lucene/MultiIndex.java
===================================================================
--- src/main/java/org/apache/jackrabbit/core/query/lucene/MultiIndex.java	(revision 801238)
+++ src/main/java/org/apache/jackrabbit/core/query/lucene/MultiIndex.java	(working copy)
@@ -715,7 +715,7 @@
      * @return an <code>IndexReader</code>.
      * @throws IOException if an error occurs constructing the <code>IndexReader</code>.
      */
-    public CachingMultiIndexReader getIndexReader(boolean initCache) throws IOException {
+    public synchronized CachingMultiIndexReader getIndexReader(boolean initCache) throws IOException {
         synchronized (updateMonitor) {
             if (multiReader != null) {
                 multiReader.acquire();