NGINX and websocket endpoint

I am trying to configure nginx as reverse proxy that does authentication
and websockets. It proxy-passes request
to apache (/auth/wsgi) for authentication - once that succeeds, it then
proxy passes to the websocked backend,
which is a java based websocket endpoint on tomcat 8.

location /basic/alerting/websocket {

        auth_request /auth/wsgi;

        proxy_http_version 1.1;
                proxy_set_header Upgrade "Websocket";
        proxy_set_header Connection "upgrade";
        proxy_set_header Host $http_host;


The authentication on apache succeeds. However, on the backend tomcat, I
get this error:

12572237 [http-nio-8080-exec-10] ERROR -
handleWebSocketVersionNotSupported() Handshake failed due to unsupported
WebSocket version: null. Supported versions: [13]

It seems that failure is because the backend is expecting the header
(“Sec-WebSocket-Version”) which is not getting passed through. I even
see in the nginx logs:

2015/03/17 17:28:12 [debug] 20261#0: *718 http proxy header:
“Sec-WebSocket-Version: 13”

Is there anything I need to do in the nginx config? Very much appreciate
your help.

NOTICE: This email message is for the sole use of the intended
recipient(s) and may contain confidential and privileged information.
Any unauthorized use, disclosure or distribution is prohibited. If you
are not the intended recipient, please contact the sender by reply email
and destroy all copies of the original message.