diff --git a/youtube_dl/extractor/npo.py b/youtube_dl/extractor/npo.py
index eafce4b84a..ff21533874 100644
--- a/youtube_dl/extractor/npo.py
+++ b/youtube_dl/extractor/npo.py
@@ -233,7 +233,7 @@ def add_format_url(format_url):
                     quality = quality_from_format_id(format_id)
                     f_id = format_id
                 else:
-                    quality, f_id = None
+                    quality, f_id = [None] * 2
                 formats.append({
                     'url': format_url,
                     'format_id': f_id,