--- asterisk-1.6.2.9/channels/chan_sip.c.orig	2010-06-22 21:22:16.000000000 -0400
+++ asterisk-1.6.2.9/channels/chan_sip.c	2010-06-22 21:24:10.000000000 -0400
@@ -7471,12 +7471,13 @@
  
 	/* See if the method is capable of creating a dialog */
 	if (sip_methods[intended_method].can_create == CAN_CREATE_DIALOG) {
+		const char *event = get_header(req, "Event");
 		if (intended_method == SIP_REFER) {
 			/* We do support REFER, but not outside of a dialog yet */
 			transmit_response_using_temp(callid, sin, 1, intended_method, req, "603 Declined (no dialog)");
-		} else if (intended_method == SIP_NOTIFY) {
-			/* We do not support out-of-dialog NOTIFY either,
-		   	like voicemail notification, so cancel that early */
+		} else if (intended_method == SIP_NOTIFY && (!event || strcmp(event, "keep-alive"))) {
+			/* We do not support out-of-dialog NOTIFY either, unless it is a
+			 * keep-alive, like voicemail notification, so cancel that early */
 			transmit_response_using_temp(callid, sin, 1, intended_method, req, "489 Bad event");
 		} else {
 			/* Ok, time to create a new SIP dialog object, a pvt */