why didn't ldap client validate ssl certificate?

hi, I have a question on using tls on ldap. Hopefully anybody could give a hint on this.

On the client side,I have set the TLS_REQCERT as demand. The TLS_CACERTDIR is also set, but I didn't put any certificate in the directory.

To my surprise, even though no certificate is provided, ldapsearch could still succeed returning the data.

Is this a bug?

the openldap is running on redhat enterprise linux 4, openldap version is openldap-servers-sql-2.2.13-12.el4 openldap-servers-2.2.13-12.el4 openldap-devel-2.2.13-12.el4 openldap-2.2.13-12.el4 openldap-clients-2.2.13-12.el4

Any idea is appreciated!

Thanks lei