How to force Jetty to ask for credentials after invalidating the session?

Question

I'm using jetty 6.1.22 with BASIC authentication as my login mechanism. The first time I log into the web app, the browser requests the username and password.

If it try to log out using a session.invalidate(), the session is invalidated but the credentials are cached. This means that if I try to connect to a secured URL, I will see a different session id but no dialog for username and password.