diff --git a/hadoop-mapreduce-project/CHANGES.txt b/hadoop-mapreduce-project/CHANGES.txt
index 7f16f6d4b97..68e3cf3722d 100644
--- a/hadoop-mapreduce-project/CHANGES.txt
+++ b/hadoop-mapreduce-project/CHANGES.txt
@@ -384,6 +384,9 @@ Release 0.23.1 - Unreleased
     MAPREDUCE-3616. Thread pool for launching containers in MR AM not
     expanding as expected. (vinodkv via sseth)
 
+    MAPREDUCE-3639. Fixed TokenCache to work with absent FileSystem canonical
+    service-names. (Siddharth Seth via vinodkv)
+
 Release 0.23.0 - 2011-11-01 
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/security/TokenCache.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/security/TokenCache.java
index c3a084d2392..9b60c33f9ae 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/security/TokenCache.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/security/TokenCache.java
@@ -172,10 +172,14 @@ public class TokenCache {
   @InterfaceAudience.Private
   public static Token<DelegationTokenIdentifier> getDelegationToken(
       Credentials credentials, String namenode) {
+    //No fs specific tokens issues by this fs. It may however issue tokens
+    // for other filesystems - which would be keyed by that filesystems name.
+    if (namenode == null)  
+      return null;
     return (Token<DelegationTokenIdentifier>) credentials.getToken(new Text(
         namenode));
   }
-  
+
   /**
    * load job token from a file
    * @param conf
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/security/TestTokenCache.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/security/TestTokenCache.java
index 5d2101b2292..8c084fe0ba6 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/security/TestTokenCache.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/security/TestTokenCache.java
@@ -130,7 +130,7 @@ public class TestTokenCache {
   private FileSystem setupMultiFs(final FileSystem singleFs,
       final String renewer, final Credentials credentials) throws Exception {
     FileSystem mockFs = mock(FileSystem.class);
-    when(mockFs.getCanonicalServiceName()).thenReturn("multifs");
+    when(mockFs.getCanonicalServiceName()).thenReturn(null);
     when(mockFs.getUri()).thenReturn(new URI("multifs:///"));
 
     when(mockFs.getDelegationTokens(any(String.class))).thenThrow(