diff --git a/src/wp-admin/menu-header.php b/src/wp-admin/menu-header.php
index 0f067f247e..11c17db3da 100644
--- a/src/wp-admin/menu-header.php
+++ b/src/wp-admin/menu-header.php
@@ -23,7 +23,7 @@ $self = preg_replace('|^.*/mu-plugins/|i', '', $self);
  * @global array  $submenu
  * @global string $parent_file
  */
-global $menu, $submenu, $parent_file;
+global $menu, $submenu, $parent_file, $submenu_file;
 
 /**
  * Filter the parent file of an admin menu sub-menu item.