Apache directive - require valid-user

in httpd.conf
<Directory "/var/www/html/phpldapadmin">
   Options FollowSymLinks
   AllowOverride Options AuthConfig
   AuthType Basic
   AuthName "LDAP Admin"
   Require valid-user
</Directory>

in /var/log/httpd/error_log
[Sat Dec 18 01:38:55 2004] [crit] [client 127.0.0.1] configuration
error:  couldn't check user.  No user file?: /phpldapadmin

Is there a way to just have it require a valid user to the system
(i.e. /etc/passwd or getent passwd) without creating a separate user
file on disk? I can't seem to get around this.

Craig