User sync auto-activates all buddypress user accounts on all sites except master site.

I installed buddypress and user sync on 1 master site, and several subsites (all single installs). When a new user registers on master site - the account gets copied ok to the subsites, and user activation is required to sign in to the master site - however, the problem is, user can instantly login to all the subsites without activation on any site including the master site. Q: how do I stop auto-activation on the subsites so that user can only login to any site only after activation on master site?