diff --git a/modules/menu/menu.module b/modules/menu/menu.module
index 3edf158..a407c37 100644
--- a/modules/menu/menu.module
+++ b/modules/menu/menu.module
@@ -246,7 +246,7 @@ function menu_load_all() {
  *
  * @param $menu
  *   An array representing a custom menu:
- *   - menu_name: The unique name of the custom menu.
+ *   - menu_name: The unique name of the custom menu ([a-z0-9-] only).
  *   - title: The human readable menu title.
  *   - description: The custom menu description.
  *