diff --git a/telethon/tl/custom/file.py b/telethon/tl/custom/file.py
index 210eb53d..aa714828 100644
--- a/telethon/tl/custom/file.py
+++ b/telethon/tl/custom/file.py
@@ -21,7 +21,12 @@ class File:
     @property
     def id(self):
         """
-        The bot-API style ``file_id`` representing this file.
+        The old bot-API style ``file_id`` representing this file.
+
+        .. warning::
+
+            This feature has not been maintained for a long time and
+            may not work. It will be removed in future versions.
 
         .. note::