I enabled that as well, and it's working, but I can't protect my admin folder.
The first rules don't work, but the statistics folder is working, odd...
<Directory "/var/www/vhosts/intranet.domain.com/subdomains/intranet/httpdocs/admin">
AuthType Basic
AuthName "admin"
AuthUserFile "/var/www/vhosts/system/intranet.domain.com/pd/d..httpdocs@admin"
require valid-user
Options +FollowSymLinks
</Directory>
<Directory "/var/www/vhosts/system/intranet.domain.com/statistics">
AuthType Basic
AuthName "Domeinstatistieken"
AuthUserFile "/var/www/vhosts/system/intranet.domain.com/pd/d..httpdocs@plesk-stat"
require valid-user
Options +FollowSymLinks
</Directory>