--- a/dwm.c	Mon Mar 17 17:33:25 2008 +0000
+++ b/dwm.c	Mon Mar 17 23:45:46 2008 +0000
@@ -259,7 +259,7 @@
 	XGetClassHint(dpy, c->win, &ch);
 	for(i = 0; i < LENGTH(rules); i++) {
 		r = &rules[i];
-		if(strstr(c->name, r->title)
+		if(r->title && strstr(c->name, r->title)
 		|| (ch.res_class && r->class && strstr(ch.res_class, r->class))
 		|| (ch.res_name && r->instance && strstr(ch.res_name, r->instance)))
 		{