Index: src/java/org/apache/hadoop/dfs/FSNamesystem.java
===================================================================
--- src/java/org/apache/hadoop/dfs/FSNamesystem.java	(revision 664107)
+++ src/java/org/apache/hadoop/dfs/FSNamesystem.java	(working copy)
@@ -3948,7 +3948,7 @@
     /**
      */
     public void run() {
-      while (fsRunning && !safeMode.canLeave()) {
+      while (fsRunning && (safeMode != null && !safeMode.canLeave())) {
         try {
           Thread.sleep(recheckInterval);
         } catch (InterruptedException ie) {