--- ./rpmio/macro.c.unchecked-eol	2005-11-12 02:18:23.000000000 +0100
+++ ./rpmio/macro.c	2006-06-17 16:12:05.828106835 +0200
@@ -1256,7 +1256,7 @@
 	chkexist = 0;
 	switch ((c = *s)) {
 	default:		/* %name substitution */
-		while (strchr("!?", *s) != NULL) {
+		while (*s && strchr("!?", *s) != NULL) {
 			switch(*s++) {
 			case '!':
 				negate = ((negate + 1) % 2);