diff --git a/src/java/org/apache/lucene/index/IndexWriter.java b/src/java/org/apache/lucene/index/IndexWriter.java
index 108aba3286d..469bfe0b28f 100644
--- a/src/java/org/apache/lucene/index/IndexWriter.java
+++ b/src/java/org/apache/lucene/index/IndexWriter.java
@@ -1269,7 +1269,7 @@ public class IndexWriter {
    *  the writer was opened with <code>autoCommit=true</code>.
    * @throws IOException if there is a low-level IO error
    */
-  public void abort() throws IOException {
+  public synchronized void abort() throws IOException {
     ensureOpen();
     if (!autoCommit) {