diff --git a/yt_dlp/extractor/nexx.py b/yt_dlp/extractor/nexx.py
index a30108483..8aceebd49 100644
--- a/yt_dlp/extractor/nexx.py
+++ b/yt_dlp/extractor/nexx.py
@@ -385,8 +385,7 @@ def find_video(result):
         elif cdn == 'free':
             formats = self._extract_free_formats(video, video_id)
         else:
-            # TODO: reverse more cdns
-            assert False
+            self.raise_no_formats(f'{cdn} formats are currently not supported', video_id)
 
         self._sort_formats(formats)