LDAP / Active directory

I am running Tiki version 8.3. I have TW configured to use LDAP/Active Directory for authentication. TW connects to LDAP, authenticates, creates Tiki account and logs the user in. All seems to work well,however, if a user changes their password on the LDAP side they are able to log in with their old and new password. Is this behavior expected or is there something I can configure to delegate authentication completely to LDAP. Thank you for your time.