diff --git a/youtube_dl/extractor/youtube.py b/youtube_dl/extractor/youtube.py
index 5406de50b4..cea3d5c951 100644
--- a/youtube_dl/extractor/youtube.py
+++ b/youtube_dl/extractor/youtube.py
@@ -510,7 +510,7 @@ def _genslice(start, end, step):
 
     def _parse_sig_js(self, jscode):
         funcname = self._search_regex(
-            r'signature=([$a-zA-Z]+)', jscode,
+            r'\.sig\|\|([a-zA-Z0-9]+)\(', jscode,
              'Initial JS player signature function name')
 
         jsi = JSInterpreter(jscode)