diff --git a/IPython/external/ssh/tunnel.py b/IPython/external/ssh/tunnel.py
index 6aa3f2d..0cf9bcb 100644
--- a/IPython/external/ssh/tunnel.py
+++ b/IPython/external/ssh/tunnel.py
@@ -214,7 +214,7 @@ def openssh_tunnel(lport, rport, server, remoteip='127.0.0.1', keyfile=None, pas
         server, port = server.split(':')
         ssh += " -p %s" % port
         
-    cmd = "%s -f -L 127.0.0.1:%i:%s:%i %s sleep %i" % (
+    cmd = "%s -f -S none -L 127.0.0.1:%i:%s:%i %s sleep %i" % (
         ssh, lport, remoteip, rport, server, timeout)
     tunnel = pexpect.spawn(cmd)
     failed = False