diff --git a/core/src/main/scala/spark/scheduler/mesos/MesosSchedulerBackend.scala b/core/src/main/scala/spark/scheduler/mesos/MesosSchedulerBackend.scala
index cdfe1f25634854b4eea2168294453706a64de542..814443fa52745a11fab771cf8de6a28bb90e792e 100644
--- a/core/src/main/scala/spark/scheduler/mesos/MesosSchedulerBackend.scala
+++ b/core/src/main/scala/spark/scheduler/mesos/MesosSchedulerBackend.scala
@@ -272,7 +272,7 @@ private[spark] class MesosSchedulerBackend(
     synchronized {
       slaveIdsWithExecutors -= slaveId.getValue
     }
-    scheduler.slaveLost(slaveId.toString)
+    scheduler.slaveLost(slaveId.getValue)
   }
 
   override def executorLost(d: SchedulerDriver, e: ExecutorID, s: SlaveID, status: Int) {