diff --git a/IPython/html/base/zmqhandlers.py b/IPython/html/base/zmqhandlers.py
index 8d7a2dc..4ddcb5e 100644
--- a/IPython/html/base/zmqhandlers.py
+++ b/IPython/html/base/zmqhandlers.py
@@ -94,6 +94,19 @@ if os.environ.get('IPYTHON_ALLOW_DRAFT_WEBSOCKETS_FOR_PHANTOMJS', False):
class ZMQStreamHandler(WebSocketHandler):
+ if tornado.version_info < (4,1):
+ """Backport send_error from tornado 4.1 to 4.0"""
+ def send_error(self, *args, **kwargs):
+ if self.stream is None:
+ super(WebSocketHandler, self).send_error(*args, **kwargs)
+ else:
+ # If we get an uncaught exception during the handshake,
+ # we have no choice but to abruptly close the connection.
+ # TODO: for uncaught exceptions after the handshake,
+ # we can close the connection more gracefully.
+ self.stream.close()
+
+
def check_origin(self, origin):
"""Check Origin == Host or Access-Control-Allow-Origin.