[Users] mediaproxy working, but not if asterisk is involved

hi my users subscribe with openser, en asterisk is used as connectivity to pstn i am now installing a mediaproxy, for all users, so every call goes via a mediaproxy. I'm doing this as follows (relevant statements only) in route #I installed the t_on_reply here to be sure that every reply gets parsed, but normally in the INVITE section should be enough? t_on_reply("1"); if (method==INVITE) { use_media_proxy(); } onreply_route[1] { log(-3,"reply received"); if (!search("^Content-Length:[ ]*0")) { log(-3,"using mediaproxy"); use_media_proxy(); }; } the weird is, for all local users, this works fine, but as soon as asterisk is involved, the reply doesn't get triggered (not seeing the "reply received" either, only when disconnecting the call). The call get's established fine, asterisk is sending media to the mediaproxy, but the SDP towards the calling phone is not modified (since the onreply isn't triggered) am I missing something here? thanks Arne