Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(revision 7840)
+++ channels/chan_sip.c	(working copy)
@@ -1830,7 +1830,9 @@
 /*! \brief  create_addr_from_peer: create address structure from peer reference ---*/
 static int create_addr_from_peer(struct sip_pvt *r, struct sip_peer *peer)
 {
-	char *callhost;
+	char tmpcall[256];
+	char *pos;
+	int len;
 
 	if ((peer->addr.sin_addr.s_addr || peer->defaddr.sin_addr.s_addr) &&
 	    (!peer->maxms || ((peer->lastms >= 0)  && (peer->lastms <= peer->maxms)))) {
@@ -1867,8 +1869,14 @@
 	ast_string_field_set(r, tohost, peer->tohost);
 	ast_string_field_set(r, fullcontact, peer->fullcontact);
 	if (!r->initreq.headers && !ast_strlen_zero(peer->fromdomain)) {
-		if ((callhost = strchr(r->callid, '@'))) {
-			strncpy(callhost + 1, peer->fromdomain, sizeof(r->callid) - (callhost - r->callid) - 2);
+		if ((pos = strchr(r->callid, '@'))) {
+			pos[0]=0;
+			len=strlen(r->callid);
+			if(len > sizeof(tmpcall)) 
+				len=sizeof(tmpcall)-1;
+			strncpy(tmpcall, r->callid, len);
+			tmpcall[len]= 0;
+			ast_string_field_build(r, callid, "%s@%s", tmpcall, peer->fromdomain);
 		}
 	}
 	if (ast_strlen_zero(r->tohost)) {