Can Simultaneous-Use be used with EAP-TLS?

I am using EAP-TLS for authentication so I have no use for a backend db to check username/password credentials. However, I would still like to prevent simultaneous logins with the same certificate. Is this possible without having an sql database? I have "Simultaneous-Users := 1" set in the "users" configuration file but it doesn't seem to do anything. Clients are being checked against this line in "users" DEFAULT Simultaneous-Use :=1