--- a/src/devices/wifi/mac-low.cc	Wed Apr 22 21:40:06 2009 +0400
+++ b/src/devices/wifi/mac-low.cc	Wed Apr 29 13:06:06 2009 +0400
@@ -271,6 +271,7 @@
 MacLow::DoDispose (void)
 {
   NS_LOG_FUNCTION (this);
+  m_listener = 0;
   CancelAllEvents ();
   m_phy = 0;
   m_stationManager = 0;