diff --git a/youtube_dl/jsinterp.py b/youtube_dl/jsinterp.py
index 9d4a5bc57..c18c4fef1 100644
--- a/youtube_dl/jsinterp.py
+++ b/youtube_dl/jsinterp.py
@@ -985,9 +985,9 @@ class JSInterpreter(object):
                 \((?P<args>[^)]*)\)\s*
                 (?P<code>{.+})''' % {'name': re.escape(funcname)},
             self.code)
-        code, _ = self._separate_at_paren(func_m.group('code'))  # refine the match
         if func_m is None:
             raise self.Exception('Could not find JS function "{funcname}"'.format(**locals()))
+        code, _ = self._separate_at_paren(func_m.group('code'))  # refine the match
         return self.build_arglist(func_m.group('args')), code
 
     def extract_function(self, funcname):