diff --git a/telebot/apihelper.py b/telebot/apihelper.py
index 1cc57ab..2fe3a7d 100644
--- a/telebot/apihelper.py
+++ b/telebot/apihelper.py
@@ -830,9 +830,11 @@ def pin_chat_message(token, chat_id, message_id, disable_notification=None):
     return _make_request(token, method_url, params=payload, method='post')
 
 
-def unpin_chat_message(token, chat_id, message_id=None):
+def unpin_chat_message(token, chat_id, message_id):
     method_url = 'unpinChatMessage'
-    payload = {'chat_id': chat_id, 'message_id': message_id}
+    payload = {'chat_id': chat_id}
+    if message_id:
+        payload['message_id'] = message_id
     return _make_request(token, method_url, params=payload, method='post')