diff -up sudo-1.8.6p3/plugins/sudoers/visudo.c.aliaswarnonly sudo-1.8.6p3/plugins/sudoers/visudo.c

--- sudo-1.8.6p3/plugins/sudoers/visudo.c.aliaswarnonly	2012-09-25 16:19:04.995831784 +0200

+++ sudo-1.8.6p3/plugins/sudoers/visudo.c	2012-09-25 16:20:15.768964400 +0200

@@ -1238,7 +1238,7 @@ check_aliases(bool strict, bool quiet)

     /* If all aliases were referenced we will have an empty tree. */

     if (!no_aliases() && !quiet)

-	alias_apply(print_unused, strict ? "Error" : "Warning");

+	alias_apply(print_unused, "Warning");

     debug_return_int(strict ? errors : 0);

 }