diff --git a/src/internet-stack/tcp-socket-impl.cc b/src/internet-stack/tcp-socket-impl.cc
index 1845a62b0..1fe4f991e 100644
--- a/src/internet-stack/tcp-socket-impl.cc
+++ b/src/internet-stack/tcp-socket-impl.cc
@@ -1266,7 +1266,10 @@ void TcpSocketImpl::NewRx (Ptr<Packet> p,
   }
   else
   {
-    m_delAckEvent = Simulator::Schedule (m_delAckTimeout, &TcpSocketImpl::DelAckTimeout, this);
+    if (m_delAckEvent.IsExpired())
+    {
+      m_delAckEvent = Simulator::Schedule (m_delAckTimeout, &TcpSocketImpl::DelAckTimeout, this);
+    }
   }
 }