diff --git a/yt_dlp/extractor/twitch.py b/yt_dlp/extractor/twitch.py
index 07aeb9807..8a24160a6 100644
--- a/yt_dlp/extractor/twitch.py
+++ b/yt_dlp/extractor/twitch.py
@@ -612,7 +612,7 @@ def _extract_chat(self, vod_id):
             'live_chat': [  # subtitle tag
                 {
                     'data': json.dumps(chat_history),
-                    'ext': 'json'
+                    'ext': 'twitch-gql-20221228.json'
                 }
             ]
         }