--- a/src/wifi/model/mac-low.cc	Fri Feb 15 15:38:05 2013 -0500
+++ b/src/wifi/model/mac-low.cc	Mon Feb 18 10:35:03 2013 -0500
@@ -1704,7 +1704,10 @@
     }
   m_txParams.DisableNextData ();
 
-  StartDataTxTimers ();
+  if (!immediate)
+    {
+      StartDataTxTimers ();
+    }
 
   NS_ASSERT (duration >= MicroSeconds (0));
   hdr.SetDuration (duration);