diff --git a/telethon/client/uploads.py b/telethon/client/uploads.py
index 6f4edd04..a5eed2a4 100644
--- a/telethon/client/uploads.py
+++ b/telethon/client/uploads.py
@@ -39,7 +39,7 @@ def _resize_photo_if_needed(
             or (isinstance(file, io.IOBase) and not file.seekable())):
         return file
 
-    before = file.tell() if isinstance(file, io.IOBase) else None
+    before = file.tell() if isinstance(file, io.IOBase) else 0
     if isinstance(file, bytes):
         file = io.BytesIO(file)