[Koha] Self-Registering Patrons allowed to choose -any- patron category?

I've activated Patron Self-Registration in the Koha library I support and that seems to be working okay; Except that on the self-registration screen, the new patron is allowed to choose whatever patron category he wishes, including those that should be staff or admin only. I would prefer self-registered patrons be limited to the default patron category and only be moved to an more appropriate category after staff review. Is there a setting that allows this? thanks!