diff --git a/telethon/client/uploads.py b/telethon/client/uploads.py
index a5eed2a4..aed9b136 100644
--- a/telethon/client/uploads.py
+++ b/telethon/client/uploads.py
@@ -39,10 +39,11 @@ 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 0
     if isinstance(file, bytes):
         file = io.BytesIO(file)
 
+    before = file.tell() if isinstance(file, io.IOBase) else None
+
     try:
         # Don't use a `with` block for `image`, or `file` would be closed.
         # See https://github.com/LonamiWebs/Telethon/issues/1121 for more.