--- asterisk/channels/chan_sip.c	2005-01-05 08:15:12.000000000 -0700
+++ asterisk-20050105/channels/chan_sip.c	2005-01-05 12:06:03.000000000 -0700
@@ -3917,6 +3917,8 @@
 		}
 		mto = c;
 
+		add_header(&req, "Event", "presence");
+		add_header(&req, "Subscription-State", "active");
 		add_header(&req, "Content-Type", "application/xpidf+xml");
 
 		if ((state==AST_EXTENSION_UNAVAILABLE) || (state==AST_EXTENSION_BUSY))