diff -r asterisk-1.4.18/channels/chan_sip.c asterisk-1.4.18-mod/channels/chan_sip.c
15377a15378,15380
> 		p = find_call(&req, &sin, req.method);  /* returns p locked */
> 		if (p == NULL) return 1; /* We couldn't lock since it was removed. */
> 
15384a15388
> 		ast_mutex_unlock(&p->lock);