diff --git a/core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala b/core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala
index 61ab635842..a83762ff01 100644
--- a/core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala
+++ b/core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala
@@ -798,7 +798,11 @@ private[spark] class ExecutorAllocationManager(
         }
         if (taskEnd.taskInfo.speculative) {
           stageAttemptToSpeculativeTaskIndices.get(stageAttempt).foreach {_.remove{taskIndex}}
-          stageAttemptToNumSpeculativeTasks(stageAttempt) -= 1
+          // If the previous task attempt succeeded first and it was the last task in a stage,
+          // the stage may have been removed before handing this speculative TaskEnd event.
+          if (stageAttemptToNumSpeculativeTasks.contains(stageAttempt)) {
+            stageAttemptToNumSpeculativeTasks(stageAttempt) -= 1
+          }
         }
 
         taskEnd.reason match {