diff --git a/Lib/httplib.py b/Lib/httplib.py
index 8629cc3..e5ef8b7 100644
--- a/Lib/httplib.py
+++ b/Lib/httplib.py
@@ -658,7 +658,7 @@
         if strict is not None:
             self.strict = strict
 
-    def _set_tunnel(self, host, port=None):
+    def _set_tunnel(self, host, port=None, headers=None):
         """ Sets up the host and the port for the HTTP CONNECT Tunnelling.
 
         The headers argument should be a mapping of extra HTTP headers