[Serusers] ACK for non-2XX not record-routed

Hi, I've been using SER (0.9.6) as a Proxy doing Loose Routing between 2 endpoints. If I place a call I can see how the ACK for the 2XX response to the INVITE is properly handled (Route header removed, Record-Route inserted). Now with the call still up, I do a re-INVITE which is rejected with a 415. The re-INVITE request sent by UAC contained a Route header, as it was an in-dialog request in a record-routed dialog. Now as per RFC3261 section 17.1.1.3: If the INVITE request whose response is being acknowledged had Route header fields, those header fields MUST appear in the ACK. This is to ensure that the ACK can be routed properly through any downstream stateless proxies. My UAC complied with the above, but SER seemed to choke on this: whereas the ACK for 2XX was successfully routed by SER in the original INVITE, the ACK for non-2XX (looking exactly the same: same Request URI, same IP destination, same Route header, ... different Via branch of course) is not handled properly: yes the ACK reaches UAS but it still has the Route header in it, and no Record-Route was added. And I'm guessing that if there had been another proxy in the Route Set on the way to the UAS it would have been bypassed. SER traces for ACK-2XX: SER traces for ACK-non-2XX: This doesn't seem right, am I missing something here? Thanks, Emmanuel.