diff --git a/includes/menu.inc b/includes/menu.inc
index 8ca09984103..8d370c86897 100644
--- a/includes/menu.inc
+++ b/includes/menu.inc
@@ -2279,7 +2279,7 @@ function _menu_router_build($callbacks) {
       // Look for wildcards in the form allowed to be used in PHP functions,
       // because we are using these to construct the load function names.
       // See http://php.net/manual/en/language.functions.php for reference.
-      if (preg_match('/^%([a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)$/', $part, $matches)) {
+      if (preg_match('/^%(|[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)$/', $part, $matches)) {
         if (empty($matches[1])) {
           $match = TRUE;
           $load_functions[$k] = NULL;