diff --git a/aiogram/contrib/middlewares/i18n.py b/aiogram/contrib/middlewares/i18n.py
index 651b77de..5fca322b 100644
--- a/aiogram/contrib/middlewares/i18n.py
+++ b/aiogram/contrib/middlewares/i18n.py
@@ -135,6 +135,8 @@ class I18nMiddleware(BaseMiddleware):
         if locale:
             *_, data = args
             language = data['locale'] = locale.language
+            if language not in self.locales.keys():
+                return self.default
             return language
         return None