dovecot - Aug 2004 - Unknown setting: ssl_ca_file

I am using 0.99.10.7-1 on Debian, and I'm having some trouble with SSL. I
purchased a certificate from Thawte and I can't figure out how to tell
dovecot about the CA cert. Adding ssl_ca_file to my configuration produces
"Unknown setting: ssl_ca_file" on dovecot startup.

Postfix has a smtpd_tls_CAfile argument and that part is working fine.

Is this a Debian-specific problem or is ssl_ca_file newer than 0.99.10.7?

-- 
Jacob Elder