diff --git a/core/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosTaskLaunchData.scala b/core/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosTaskLaunchData.scala
index e983ccdcee7b5..5e7e6567a3e06 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosTaskLaunchData.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/cluster/mesos/MesosTaskLaunchData.scala
@@ -34,8 +34,8 @@ private[spark] case class MesosTaskLaunchData(
     val dataBuffer = ByteBuffer.allocate(4 + serializedTask.limit)
     dataBuffer.putInt(attemptNumber)
     dataBuffer.put(serializedTask)
-    logDebug(s"ByteBuffer size: [${dataBuffer.remaining}]")
     dataBuffer.rewind
+    logDebug(s"ByteBuffer size: [${dataBuffer.remaining}]")
     ByteString.copyFrom(dataBuffer)
   }
 }