[Serusers] Authentication of ReInvite

Morning everyone, Has anyone tried authentication of Re-INVITE on SER? When I add the proxy_challenge to the ReInvite in the SER configure file, the ACK for 407 from the client is porxied by SER to the other side. The signalling looks like: caller----------------------SER---------------------Callee ------------------ normal call setup-------------------- --------------------------blha blha----------------------- ------------------------------------------------------------- ---call hold Re-Invite---> <--- 407 challenge------ --------ACK-----------------> -------------ACK---------> *** This is not to be proxied! ----ReInvite---------------> ----------------------etc etc............ Anyone seen this while doing similar thing on SER? How can I stop SER proxing this ACK just like the way SER treat the original Invite with authentiacion? Here is the authentication part in the loose route block of my SER config file: if (method=="INVITE") { if (!proxy_authorize("test.com", "subscriber")) { proxy_challenge( "test.com", "0"); break; }; }; Thanks, Pat