--- chan_sip.c.br14.104037.original	2008-02-25 11:36:12.000000000 +0100
+++ chan_sip.c.br14.104037	2008-02-25 11:39:43.000000000 +0100
@@ -4567,7 +4567,7 @@
 			found = (!strcmp(p->callid, callid));
 		else 
 			found = (!strcmp(p->callid, callid) && 
-			(!pedanticsipchecking || !tag || ast_strlen_zero(p->theirtag) || !strcmp(p->theirtag, tag))) ;
+			(!pedanticsipchecking || ast_strlen_zero(tag) || ast_strlen_zero(p->theirtag) || !strcmp(p->theirtag, tag))) ;
 
 		if (option_debug > 4)
 			ast_log(LOG_DEBUG, "= %s Their Call ID: %s Their Tag %s Our tag: %s\n", found ? "Found" : "No match", p->callid, p->theirtag, p->tag);