diff --git a/RELEASE_NOTES b/RELEASE_NOTES
index 9113b3014..e2868f257 100644
--- a/RELEASE_NOTES
+++ b/RELEASE_NOTES
@@ -28,6 +28,7 @@ Bugs fixed
 ----------
 - Bug 1722 - beacons transmitted concurrently
 - Bug 1616 - WifiPhyStateHelper reports false CCA_BUSY times at State trace source
+- Bug 1011 - assert failed. file=../src/devices/wifi/dcf-manager.cc
 
 Release 3.18
 =============
diff --git a/src/wifi/model/dcf-manager.cc b/src/wifi/model/dcf-manager.cc
index 07e0c5a0a..51ad32caf 100644
--- a/src/wifi/model/dcf-manager.cc
+++ b/src/wifi/model/dcf-manager.cc
@@ -756,7 +756,7 @@ void
 DcfManager::NotifyNavStartNow (Time duration)
 {
   NS_LOG_FUNCTION (this << duration);
-  NS_ASSERT (m_lastNavStart < Simulator::Now ());
+  NS_ASSERT (m_lastNavStart <= Simulator::Now ());
   MY_DEBUG ("nav start for=" << duration);
   UpdateBackoff ();
   Time newNavEnd = Simulator::Now () + duration;