diff --git a/pyrogram/client/types/messages_and_media/photo_size.py b/pyrogram/client/types/messages_and_media/photo_size.py
index e1be74df..116b564c 100644
--- a/pyrogram/client/types/messages_and_media/photo_size.py
+++ b/pyrogram/client/types/messages_and_media/photo_size.py
@@ -81,6 +81,6 @@ class PhotoSize(PyrogramType):
             ),
             width=getattr(photo_size, "w", 0),
             height=getattr(photo_size, "h", 0),
-            file_size=getattr(photo_size, "size", len(photo_size.bytes)),
+            file_size=getattr(photo_size, "size", len(getattr(photo_size, "bytes", b""))),
             client=client
         )