diff --git a/src/devices/wifi/mac-low.cc b/src/devices/wifi/mac-low.cc
index 647ea4083..379a3baf3 100644
--- a/src/devices/wifi/mac-low.cc
+++ b/src/devices/wifi/mac-low.cc
@@ -948,11 +948,11 @@ MacLow::IsNavZero (void) const
 {
   if (m_lastNavStart + m_lastNavDuration > Simulator::Now ()) 
     {
-      return false;
+      return true;
     } 
   else 
     {
-      return true;
+      return false;
     }
 }