diff --git a/modules/menu/menu.module b/modules/menu/menu.module
index fc8f68a..8f2e159 100644
--- a/modules/menu/menu.module
+++ b/modules/menu/menu.module
@@ -246,7 +246,8 @@ 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 (lowercase letters,
+ *     numbers and dash '-' only).
  *   - title: The human readable menu title.
  *   - description: The custom menu description.
  *