diff --git a/youtube_dl/extractor/niconico.py b/youtube_dl/extractor/niconico.py
index dbe871f16..76b412ff1 100644
--- a/youtube_dl/extractor/niconico.py
+++ b/youtube_dl/extractor/niconico.py
@@ -252,7 +252,7 @@ class NiconicoIE(InfoExtractor):
                     },
                     'timing_constraint': 'unlimited'
                 }
-            }))
+            }).encode())
 
         resolution = video_quality.get('resolution', {})