Kerberos FALLBACK_AUTHCLASS fails with Chrome


With NAM 4.5.3 we're using the Kerberos Method configured with FALLBACK_AUTHCLASS=com.novell.nidp.authentication.local.ProtectedPasswordClass (Secure Name/Password - Form class). 

If we access a protected resource without the kerberos ticket, it works correctly with Firefox, and the user is forwarded to the "Secure Name/Password Form" login page. But with Chrome, it's presented with a basic authentication, what seems to be the Name/Password Basic class.

Any idea?