diff --git a/CHANGES.txt b/CHANGES.txt
index ace80b1cf07..fb982034747 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -47,6 +47,10 @@ Bug fixes
 
  8. LUCENE-607: ParallelReader's TermEnum fails to advance properly to
     new fields (Chuck Williams, Christian Kohlschuetter via Yonik Seeley)
+
+ 9. LUCENE-415: A previously unclean shutdown during indexing can cause
+    a non-empty segment file to be re-used, causing index corruption.
+    (Andy Hind via Yonik Seeley)
         
 Optimizations
 
diff --git a/src/java/org/apache/lucene/store/FSDirectory.java b/src/java/org/apache/lucene/store/FSDirectory.java
index 88cbe5ea457..bea618a5c4a 100644
--- a/src/java/org/apache/lucene/store/FSDirectory.java
+++ b/src/java/org/apache/lucene/store/FSDirectory.java
@@ -496,6 +496,13 @@ class FSIndexOutput extends BufferedIndexOutput {
 
   public FSIndexOutput(File path) throws IOException {
     file = new RandomAccessFile(path, "rw");
+    if (file.length() == 0) {
+      // This can happen if there was a previous crash / unclean shutdown that
+      // left files around, then we end up re-using a segment name.
+      // If we have a logging framework in the future, a warning here might be
+      // a good idea.
+      file.setLength(0);
+    }
   }
 
   /** output methods: */