diff --git a/hadoop-mapreduce-project/CHANGES.txt b/hadoop-mapreduce-project/CHANGES.txt
index 02284c19163..34cc2a462ed 100644
--- a/hadoop-mapreduce-project/CHANGES.txt
+++ b/hadoop-mapreduce-project/CHANGES.txt
@@ -543,6 +543,9 @@ Release 0.23.3 - UNRELEASED
     MAPREDUCE-4300. OOM in AM can turn it into a zombie. (Robert Evans via
     tgraves)
 
+    MAPREDUCE-4252. MR2 job never completes with 1 pending task (Tom White via
+    bobby)
+
 Release 0.23.2 - UNRELEASED
 
   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/TaskImpl.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TaskImpl.java
index c7f89f9ac58..cf5d92b4c7c 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TaskImpl.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TaskImpl.java
@@ -189,7 +189,7 @@ public abstract class TaskImpl implements Task, EventHandler<TaskEvent> {
 
     // Transitions from SUCCEEDED state
     .addTransition(TaskState.SUCCEEDED, //only possible for map tasks
-        EnumSet.of(TaskState.SCHEDULED, TaskState.FAILED),
+        EnumSet.of(TaskState.SCHEDULED, TaskState.SUCCEEDED, TaskState.FAILED),
         TaskEventType.T_ATTEMPT_FAILED, new MapRetroactiveFailureTransition())
     .addTransition(TaskState.SUCCEEDED, //only possible for map tasks
         EnumSet.of(TaskState.SCHEDULED, TaskState.SUCCEEDED),
@@ -618,7 +618,7 @@ public abstract class TaskImpl implements Task, EventHandler<TaskEvent> {
     }
   }
 
-  private void internalError(TaskEventType type) {
+  protected void internalError(TaskEventType type) {
     LOG.error("Invalid event " + type + " on Task " + this.taskId);
     eventHandler.handle(new JobDiagnosticsUpdateEvent(
         this.taskId.getJobId(), "Invalid event " + type + 
@@ -896,6 +896,16 @@ public abstract class TaskImpl implements Task, EventHandler<TaskEvent> {
 
     @Override
     public TaskState transition(TaskImpl task, TaskEvent event) {
+      if (event instanceof TaskTAttemptEvent) {
+        TaskTAttemptEvent castEvent = (TaskTAttemptEvent) event;
+        if (task.getState() == TaskState.SUCCEEDED &&
+            !castEvent.getTaskAttemptID().equals(task.successfulAttempt)) {
+          // don't allow a different task attempt to override a previous
+          // succeeded state
+          return TaskState.SUCCEEDED;
+        }
+      }
+      
       //verify that this occurs only for map task
       //TODO: consider moving it to MapTaskImpl
       if (!TaskType.MAP.equals(task.getType())) {
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskImpl.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskImpl.java
index 4ff6001bf58..af77f7dbb7a 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskImpl.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskImpl.java
@@ -20,6 +20,7 @@ package org.apache.hadoop.mapreduce.v2.app.job.impl;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
@@ -127,8 +128,13 @@ public class TestTaskImpl {
     @Override
     protected int getMaxAttempts() {
       return 100;
-    }    
-    
+    }
+
+    @Override
+    protected void internalError(TaskEventType type) {
+      super.internalError(type);
+      fail("Internal error: " + type);
+    }
   }
   
   private class MockTaskAttemptImpl extends TaskAttemptImpl {
@@ -462,5 +468,32 @@ public class TestTaskImpl {
 
     assertTaskSucceededState();
   }
+  
+  @Test
+  public void testSpeculativeTaskAttemptSucceedsEvenIfFirstFails() {
+    TaskId taskId = getNewTaskID();
+    scheduleTaskAttempt(taskId);
+    launchTaskAttempt(getLastAttempt().getAttemptId());
+    updateLastAttemptState(TaskAttemptState.RUNNING);
+
+    // Add a speculative task attempt that succeeds
+    mockTask.handle(new TaskTAttemptEvent(getLastAttempt().getAttemptId(), 
+        TaskEventType.T_ADD_SPEC_ATTEMPT));
+    launchTaskAttempt(getLastAttempt().getAttemptId());
+    commitTaskAttempt(getLastAttempt().getAttemptId());
+    mockTask.handle(new TaskTAttemptEvent(getLastAttempt().getAttemptId(), 
+        TaskEventType.T_ATTEMPT_SUCCEEDED));
+    
+    // The task should now have succeeded
+    assertTaskSucceededState();
+    
+    // Now fail the first task attempt, after the second has succeeded
+    mockTask.handle(new TaskTAttemptEvent(taskAttempts.get(0).getAttemptId(), 
+        TaskEventType.T_ATTEMPT_FAILED));
+    
+    // The task should still be in the succeeded state
+    assertTaskSucceededState();
+    
+  }
 
 }