diff --git a/yt_dlp/YoutubeDL.py b/yt_dlp/YoutubeDL.py
index f10167826..d5c0a2422 100644
--- a/yt_dlp/YoutubeDL.py
+++ b/yt_dlp/YoutubeDL.py
@@ -3550,7 +3550,7 @@ class YoutubeDL:
             reject = lambda k, v: v is None or k.startswith('__') or k in {
                 'requested_downloads', 'requested_formats', 'requested_subtitles', 'requested_entries',
                 'entries', 'filepath', '_filename', 'filename', 'infojson_filename', 'original_url',
-                'playlist_autonumber', '_format_sort_fields',
+                'playlist_autonumber',
             }
         else:
             reject = lambda k, v: False