diff --git a/pyrogram/client/types/chat_photo.py b/pyrogram/client/types/chat_photo.py
index 60ccc447..934e93fe 100644
--- a/pyrogram/client/types/chat_photo.py
+++ b/pyrogram/client/types/chat_photo.py
@@ -35,6 +35,6 @@ class ChatPhoto(Object):
     """
     ID = 0xb0700015
 
-    def __init__(self, small_file_id, big_file_id):
+    def __init__(self, small_file_id: str, big_file_id: str):
         self.small_file_id = small_file_id  # string
         self.big_file_id = big_file_id  # string