[Freeswitch-users] Hook on SIP CANCEL

Hi guys, I am using the api_hangup_hook variable to let my internal system know when a call is terminated. Every now and then my calling party cancels the SIP Invite before my dial plan is finished. IN this case FreeSWITCH properly responds with a "487 Request Terminated" However, this does not fire the command assigned to the api_hangup_hook variable. This is probably also proper since the call has not yet been established. My question is whether there is a place somewhere where I can hook into the processing of the CANCEL SIP message. Thank you Oleg