diff --git a/RELEASE_NOTES b/RELEASE_NOTES
index f5972dd05..725e29484 100644
--- a/RELEASE_NOTES
+++ b/RELEASE_NOTES
@@ -29,6 +29,7 @@ Bugs fixed
 - Bug 2126 - LrWpanNetDevice silently accepts no mobility on the node
 - Bug 2135 - TCP doesn't honor the socket's output interface
 - Bug 2136 - The usage of tid in wifi and wave module shall be "if (tid > 7)" rather than "if (tid >= 7)"
+- Bug 2138 - SimpleNetDevice could send overlapped packets.
 
 Known issues
 ------------
diff --git a/src/network/utils/simple-net-device.cc b/src/network/utils/simple-net-device.cc
index ed8926db9..3633e5acc 100644
--- a/src/network/utils/simple-net-device.cc
+++ b/src/network/utils/simple-net-device.cc
@@ -446,7 +446,7 @@ SimpleNetDevice::SendFrom (Ptr<Packet> p, const Address& source, const Address&
 
   if (m_queue->Enqueue (p))
     {
-      if (m_queue->GetNPackets () == 1)
+      if (m_queue->GetNPackets () == 1 && !TransmitCompleteEvent.IsRunning ())
         {
           p = m_queue->Dequeue ();
           p->RemovePacketTag (tag);