diff --git a/youtube_dl/extractor/niconico.py b/youtube_dl/extractor/niconico.py
index aeb3659a3..fe4ec1a43 100644
--- a/youtube_dl/extractor/niconico.py
+++ b/youtube_dl/extractor/niconico.py
@@ -476,26 +476,22 @@ class NiconicoSeriesIE(InfoExtractor):
         'url': 'https://www.nicovideo.jp/series/8253',
         'info_dict': {
             'id': '8253',
-            'title' : '弦巻マキと結月ゆかりの未確認ゲーム日和',
+            'title': '弦巻マキと結月ゆかりの未確認ゲーム日和',
         },
-        'playlist_mincount':49,
+        'playlist_mincount': 49,
     }
     def _real_extract(self, url):
-        series_id=url.split('/')[-1]
-        webpage=self._download_webpage(url, series_id)
-        entries=re.findall(r'(?<=<a href="\/watch\/)[^"]*',webpage)
-        entries=[{
-            '_type':'url',
-            'ie_key':NiconicoIE.ie_key(),
-
-'url':('https://www.nicovideo.jp/watch/sm%s' %
-                entry),
+        series_id = url.split('/')[-1]
+        webpage = self._download_webpage(url, series_id)
+        entries = re.findall(r'<a href=["\'](\/watch\/[^"\']*)', webpage)
+        entries = [{
+            '_type': 'url',
+            'ie_key': NiconicoIE.ie_key(),
+            'url': ('https://www.nicovideo.jp%s' % entry),
         } for entry in entries]
         return {
             '_type': 'playlist',
             'id': u'8253',
             'entries': entries,
-            'title': self._search_regex(r'bodyTitle">(.*?)</div>',webpage,'title'),
+            'title': self._search_regex(r'bodyTitle">(.*?)</div>', webpage, 'title'),
         }
-
-