diff --git a/src/devices/wifi/dcf-manager.cc b/src/devices/wifi/dcf-manager.cc
index d556c1385..815f209a7 100644
--- a/src/devices/wifi/dcf-manager.cc
+++ b/src/devices/wifi/dcf-manager.cc
@@ -16,6 +16,11 @@ namespace ns3 {
  *      Implement the DCF state holder
  ****************************************************************/
 
+DcfState::DcfState ()
+  : m_backoffSlots (0),
+    m_backoffStart (Seconds (0.0))
+{}
+
 DcfState::~DcfState ()
 {}
 
@@ -30,6 +35,7 @@ DcfState::SetCwBounds (uint32_t minCw, uint32_t maxCw)
 {
   m_cwMin = minCw;
   m_cwMax = maxCw;
+  ResetCw ();
 }
 
 void 
diff --git a/src/devices/wifi/dcf-manager.h b/src/devices/wifi/dcf-manager.h
index b9ee1fce3..f78b8580b 100644
--- a/src/devices/wifi/dcf-manager.h
+++ b/src/devices/wifi/dcf-manager.h
@@ -11,6 +11,8 @@ class MacParameters;
 class DcfState
 {
 public:
+  DcfState ();
+
   virtual ~DcfState ();
 
   void SetAifsn (uint32_t aifsn);