[Users] Can openser put a Contact header in a response when behave as UAS?

Hi, I want to use the openser as a UAS on behalf of a user that's not registered. There's a proxy in the middle that receives an INVITE and find that the user is not registered, and rely the INVITE to the openser. I want the openser to send a 200 OK response, but also to put a Contact in the response so the final ACK will be send also to the openser. I have tried the following: append_hf("Contact: xxxxx:pp"); if (t_newtran()) { xlog("UAS logic"); append_hf("Contact: xxxxx:pp"); t_reply("200","OK"); append_hf("Contact: xxxxx:pp"); } else sl_reply_error(); But still no Contact appears in the 200 OK response. Thanks