diff --git a/yt_dlp/utils.py b/yt_dlp/utils.py
index e64d35936..db355ec92 100644
--- a/yt_dlp/utils.py
+++ b/yt_dlp/utils.py
@@ -3501,8 +3501,8 @@ def get_compatible_ext(*, vcodecs, acodecs, vexts, aexts, preferences=None):
         },
     }
 
-    sanitize_codec = functools.partial(try_get, getter=lambda x: x.split('.')[0].replace('0', ''))
-    vcodec, acodec = sanitize_codec(vcodecs[0]), sanitize_codec(acodecs[0])
+    sanitize_codec = functools.partial(try_get, getter=lambda x: x[0].split('.')[0].replace('0', ''))
+    vcodec, acodec = sanitize_codec(vcodecs), sanitize_codec(acodecs)
 
     for ext in preferences or COMPATIBLE_CODECS.keys():
         codec_set = COMPATIBLE_CODECS.get(ext, set())