--- a/src/test/ns3tcp/ns3tcp-cwnd-test-suite.cc	Sun Feb 05 15:13:34 2017 -0800
+++ b/src/test/ns3tcp/ns3tcp-cwnd-test-suite.cc	Sun Feb 05 18:01:38 2017 -0800
@@ -496,6 +496,8 @@
   // Create the socket for n0
   Address sinkAddress (InetSocketAddress (ipInterfs.GetAddress (1), servPort));
   Ptr<Socket> ns3TcpSocket = Socket::CreateSocket (n0n1.Get (0), TcpSocketFactory::GetTypeId ());
+  // Disable SACK because this test is testing NewReno behavior
+  ns3TcpSocket->SetAttribute ("Sack", BooleanValue (false));
   ns3TcpSocket->TraceConnectWithoutContext ("CongestionWindow", MakeCallback (&Ns3TcpCwndTestCase2::CwndChange, this));
 
   // Create and start the app for n0