diff --git a/hadoop-mapreduce-project/CHANGES.txt b/hadoop-mapreduce-project/CHANGES.txt
index e9732b8922..449c93c5e0 100644
--- a/hadoop-mapreduce-project/CHANGES.txt
+++ b/hadoop-mapreduce-project/CHANGES.txt
@@ -297,6 +297,10 @@ Release 2.5.0 - UNRELEASED
     MAPREDUCE-5868. Fixed an issue with TestPipeApplication that was causing the
     nightly builds to fail. (Akira Ajisaka via vinodkv)
 
+    MAPREDUCE-5517. Fixed MapReduce ApplicationMaster to not validate reduce side
+    resource configuration for deciding uber-mode on map-only jobs. (Siqi Li via
+    vinodkv)
+
 Release 2.4.1 - 2014-06-23 
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/job/impl/JobImpl.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/job/impl/JobImpl.java
index f8b1fd0a51..19dbb05c71 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/job/impl/JobImpl.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/job/impl/JobImpl.java
@@ -1218,22 +1218,25 @@ private void makeUberDecision(long dataInputLength) {
     boolean smallNumReduceTasks = (numReduceTasks <= sysMaxReduces);
     boolean smallInput = (dataInputLength <= sysMaxBytes);
     // ignoring overhead due to UberAM and statics as negligible here:
+    long requiredMapMB = conf.getLong(MRJobConfig.MAP_MEMORY_MB, 0);
+    long requiredReduceMB = conf.getLong(MRJobConfig.REDUCE_MEMORY_MB, 0);
+    long requiredMB = Math.max(requiredMapMB, requiredReduceMB);
+    int requiredMapCores = conf.getInt(
+            MRJobConfig.MAP_CPU_VCORES, 
+            MRJobConfig.DEFAULT_MAP_CPU_VCORES);
+    int requiredReduceCores = conf.getInt(
+            MRJobConfig.REDUCE_CPU_VCORES, 
+            MRJobConfig.DEFAULT_REDUCE_CPU_VCORES);
+    int requiredCores = Math.max(requiredMapCores, requiredReduceCores);    
+    if (numReduceTasks == 0) {
+      requiredMB = requiredMapMB;
+      requiredCores = requiredMapCores;
+    }
     boolean smallMemory =
-        ( (Math.max(conf.getLong(MRJobConfig.MAP_MEMORY_MB, 0),
-            conf.getLong(MRJobConfig.REDUCE_MEMORY_MB, 0))
-            <= sysMemSizeForUberSlot)
-            || (sysMemSizeForUberSlot == JobConf.DISABLED_MEMORY_LIMIT));
-    boolean smallCpu =
-        (
-            Math.max(
-                conf.getInt(
-                    MRJobConfig.MAP_CPU_VCORES, 
-                    MRJobConfig.DEFAULT_MAP_CPU_VCORES), 
-                conf.getInt(
-                    MRJobConfig.REDUCE_CPU_VCORES, 
-                    MRJobConfig.DEFAULT_REDUCE_CPU_VCORES)) 
-             <= sysCPUSizeForUberSlot
-        );
+        (requiredMB <= sysMemSizeForUberSlot)
+        || (sysMemSizeForUberSlot == JobConf.DISABLED_MEMORY_LIMIT);
+    
+    boolean smallCpu = requiredCores <= sysCPUSizeForUberSlot;
     boolean notChainJob = !isChainJob(conf);
 
     // User has overall veto power over uberization, or user can modify
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestJobImpl.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestJobImpl.java
index 6cfc83ea00..65352b75ad 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestJobImpl.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestJobImpl.java
@@ -657,6 +657,15 @@ public void testUberDecision() throws Exception {
     conf.setInt(MRJobConfig.JOB_UBERTASK_MAXMAPS, 1);
     isUber = testUberDecision(conf);
     Assert.assertFalse(isUber);
+    
+ // enable uber mode of 0 reducer no matter how much memory assigned to reducer
+    conf = new Configuration();
+    conf.setBoolean(MRJobConfig.JOB_UBERTASK_ENABLE, true);  
+    conf.setInt(MRJobConfig.NUM_REDUCES, 0);           
+    conf.setInt(MRJobConfig.REDUCE_MEMORY_MB, 2048);
+    conf.setInt(MRJobConfig.REDUCE_CPU_VCORES, 10);
+    isUber = testUberDecision(conf);
+    Assert.assertTrue(isUber);
   }
 
   private boolean testUberDecision(Configuration conf) {