diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/ApplicationMasterServiceTestBase.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/ApplicationMasterServiceTestBase.java
index 0b713e7739..80dbb8490e 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/ApplicationMasterServiceTestBase.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/ApplicationMasterServiceTestBase.java
@@ -382,6 +382,7 @@ protected Dispatcher createDispatcher() {
       for (int i = 0; i < 10; i++) {
         am1.unregisterAppAttempt(req, false);
       }
+      rm.drainEvents();
       Assert.assertEquals("Expecting only one event", 1,
           dispatcher.getEventCount());
     } finally {