diff --git a/yt_dlp/extractor/youtube/pot/_provider.py b/yt_dlp/extractor/youtube/pot/_provider.py
index af7034d22..02f0b8b85 100644
--- a/yt_dlp/extractor/youtube/pot/_provider.py
+++ b/yt_dlp/extractor/youtube/pot/_provider.py
@@ -117,7 +117,7 @@ def _configuration_arg(self, key, default=NO_DEFAULT, *, casesense=False):
         val = traverse_obj(self.settings, key)
         if val is None:
             return [] if default is NO_DEFAULT else default
-        return list(val) if casesense else [x.lower() for x in val]
+        return list(val) if casesense else [x.casefold() for x in val]
 
 
 class BuiltinIEContentProvider(IEContentProvider, abc.ABC):