diff --git a/src/internet-node/tcp-header.cc b/src/internet-node/tcp-header.cc
index ff06b06e6..f5920c355 100644
--- a/src/internet-node/tcp-header.cc
+++ b/src/internet-node/tcp-header.cc
@@ -44,7 +44,7 @@ TcpHeader::TcpHeader ()
     m_ackNumber (0),
     m_length (5),
     m_flags (0),
-    m_windowSize (0),
+    m_windowSize (0xffff),
     m_checksum (0),
     m_urgentPointer (0)
 {}