diff --git a/resource-managers/mesos/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosProtoUtils.scala b/resource-managers/mesos/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosProtoUtils.scala
index e08813928c34f..f816c61c53143 100644
--- a/resource-managers/mesos/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosProtoUtils.scala
+++ b/resource-managers/mesos/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosProtoUtils.scala
@@ -85,7 +85,10 @@ object MesosProtoUtils extends Logging {
       i += 1
     }
 
-    addLabel()
+    if (key.isDefined) {
+      addLabel()
+    }
+
     labels
   }
 }