diff --git a/classes/Category.php b/classes/Category.php
index 5a99f7aa3..0ba3501f4 100644
--- a/classes/Category.php
+++ b/classes/Category.php
@@ -1289,7 +1289,7 @@ class CategoryCore extends ObjectModel
 		'.(($active) ? 'AND `active` = 1': ''));
 	}
 
-	public function getCategoriesWithoutParent()
+	public static function getCategoriesWithoutParent()
 	{
 		return Db::getInstance(_PS_USE_SQL_SLAVE_)->executeS('
 		SELECT c.*