[Serusers] Problem with TCP/UDP translation

Hello I have a problem when two clients (one using UDP and one using TCP) connect to SER (version 0.8.13-dev-23). My scenario is more or less like this: TCP Client <----> SER <----> UDP Client There are no NATs or Firewalls in scene. I want to reuse the TCP connection of the TCP Client for the whole SIP signalling, so I have added the command force_tcp_alias(); to ser.cfg and changed tcp_conn.h as advised in http://lists.iptel.org/pipermail/serusers/2004-May/008262.html. The TCP Client starts the call with an INVITE and everything works correctly. However, when the UDP Client tries to send a MESSAGE, SER doesn't route the MESSAGE through the TCP connection (it sends it over UDP with the TCP port included in TCP Clients Contact!). Can anyone tell me what is misconfigured? Lots of thanks to everyone. DANIEL