Hi, I'm using t_reply if onreply_route as follow: route { ... t_on_reply("ERROR"); ... t_relay(); } onreply_route[ERROR] { t_reply("500", "Error"); } I have this call flow: CLIENT KAMAILIO CARRIER |--- INVITE ---> | |---- INVITE --->| |<---- 100 ------| |<--- 100 --------| |<---- 503 ------| |---- ACK ------>| |<--- 500 --------| |---- ACK ------->| |---- CANCEL --->| |<--- 487 -------| Kamailio sends a CANCEL message to a branch terminated by the carrier. I'm not sure it is the good way to fix this issue (espacially in use cases involving multiple branches) but here is a patch that work for me on current master: diff --git a/modules/tm/t_reply.c b/modules/tm/t_reply.c index b2e6e53..4b9e142 100644 --- a/modules/tm/t_reply.c +++ b/modules/tm/t_reply.c @@ -571,7 +571,7 @@ static int _reply_light( struct cell *trans, char* buf, unsigned int len, } } cleanup_uac_timers( trans ); - if (is_invite(trans)){ + if (is_invite(trans && get_route_type() != TM_ONREPLY_ROUTE)){ prepare_to_cancel(trans, &cancel_data.cancel_bitmap, 0); #ifdef CANCEL_REASON_SUPPORT cancel_data.reason.cause=code; --- Reply to this email directly or view it on GitHub: https://github.com/kamailio/kamailio/issues/315