diff --git a/src/MD_STD.php b/src/MD_STD.php
index a3500b2..82e9694 100644
--- a/src/MD_STD.php
+++ b/src/MD_STD.php
@@ -342,7 +342,7 @@ final class MD_STD {
      *
      * @return string
      */
-    public function get_user_lang(array $allowed_langs, string $default_lang):string {
+    public static function get_user_lang(array $allowed_langs, string $default_lang):string {
 
         $cookie_options = [
             'expires' => self::strtotime("+1 month"),