--- a/src/devices/wifi/mac-low.cc	Mon Sep 08 13:13:09 2008 -0700
+++ b/src/devices/wifi/mac-low.cc	Mon Sep 08 14:37:54 2008 -0700
@@ -1141,6 +1141,7 @@
   ack.SetType (WIFI_MAC_CTL_ACK);
   ack.SetDsNotFrom ();
   ack.SetDsNotTo ();
+  ack.SetNoRetry ();
   ack.SetNoMoreFragments ();
   ack.SetAddr1 (source);
   duration -= GetAckDuration (source, dataTxMode);