diff --git a/yt_dlp/extractor/common.py b/yt_dlp/extractor/common.py
index 187f73e7b9..432db9daf8 100644
--- a/yt_dlp/extractor/common.py
+++ b/yt_dlp/extractor/common.py
@@ -3489,7 +3489,7 @@ class InfoExtractor:
                 continue
             urls.add(source_url)
             source_type = source.get('type') or ''
-            ext = mimetype2ext(source_type) or determine_ext(source_url)
+            ext = determine_ext(source_url, default_ext=mimetype2ext(source_type))
             if source_type == 'hls' or ext == 'm3u8' or 'format=m3u8-aapl' in source_url:
                 formats.extend(self._extract_m3u8_formats(
                     source_url, video_id, 'mp4', entry_protocol='m3u8_native',