diff --git a/youtube_dl/extractor/youtube.py b/youtube_dl/extractor/youtube.py
index 63597dd16..7a909da87 100644
--- a/youtube_dl/extractor/youtube.py
+++ b/youtube_dl/extractor/youtube.py
@@ -1006,7 +1006,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
 
     def _parse_sig_js(self, jscode):
         funcname = self._search_regex(
-            r'\.sig\|\|([a-zA-Z0-9$]+)\(', jscode,
+            r'"signature",\s?([a-zA-Z0-9$]+)\(', jscode,
             'Initial JS player signature function name')
 
         jsi = JSInterpreter(jscode)