DenyUsers option on OpenS

Folks,

On a Fujitsu-Siemens PrimePower 650 running Solaris 8, I'm trying to
deny ssh access to a specific user with the DenyUsers option in
sshd_config.

The line looks (pretty simply):
DenyUsers valerio

I have since killed -HUP the sshd pid, but I am still able to login as
user valerio.

Any idea what I am doing wrong or how to troubleshoot this?

Thanks in advance

Loris