Index: channels/chan_pjsip.c
===================================================================
--- channels/chan_pjsip.c	(revision 398213)
+++ channels/chan_pjsip.c	(working copy)
@@ -2115,6 +2115,7 @@
 
 	ast_sip_session_unregister_supplement(&chan_pjsip_supplement);
 	ast_sip_session_unregister_supplement(&pbx_start_supplement);
+	ast_sip_session_unregister_supplement(&chan_pjsip_ack_supplement);
 
 	ast_custom_function_unregister(&chan_pjsip_dial_contacts_function);
 	ast_channel_unregister(&chan_pjsip_tech);