diff --git a/youtube_dl/extractor/youtube.py b/youtube_dl/extractor/youtube.py
index a346f4c96..73a01107d 100644
--- a/youtube_dl/extractor/youtube.py
+++ b/youtube_dl/extractor/youtube.py
@@ -493,6 +493,8 @@ def _get_available_subtitles(self, video_id, webpage):
         sub_lang_list = {}
         for l in lang_list:
             lang = l[1]
+            if lang in sub_lang_list:
+                continue
             params = compat_urllib_parse.urlencode({
                 'lang': lang,
                 'v': video_id,