diff --git a/src/wifi/model/txop.cc b/src/wifi/model/txop.cc
index c630d99a0..a71d27de5 100644
--- a/src/wifi/model/txop.cc
+++ b/src/wifi/model/txop.cc
@@ -102,6 +102,7 @@ Txop::DoDispose (void)
   m_stationManager = 0;
   m_rng = 0;
   m_txMiddle = 0;
+  m_channelAccessManager = 0;
 }
 
 void