--- a/src/internet/model/tcp-socket-base.cc	Fri Jan 30 16:27:50 2015 -0800
+++ b/src/internet/model/tcp-socket-base.cc	Sat Jan 31 13:20:37 2015 +0100
@@ -2025,7 +2025,7 @@
     }
 
   // Notify the application of the data being sent unless this is a retransmit
-  if (seq == m_nextTxSequence)
+  if (seq == m_highTxMark)
     {
       Simulator::ScheduleNow (&TcpSocketBase::NotifyDataSent, this, sz);
     }