Kibana 4 behind reverse proxy with URL "directory" prefix

We have to run Kibana 4 behind a reverse proxy, using Apache, due to Single-Sign-On requirements. I have set up a reverse-proxy for the prefix k4/ to proxy out to localhost:5601. The URLs come back without the prefix, and I'm wondering if there's some place in config.yml or app.js or such, where I can set the /k4 prefix for URL composition.

At least Kibana 4.1 works fine behind a reverse proxy. I have the following in my Apache configuration:

ProxyPass /kibana4/ http://localhost:5601/
ProxyPassReverse /kibana4/ http://localhost:5601/

The trailing slashes are significant.

Indeed they were! Thank you, that fixed this problem!