Facebook signup grants admin accounts when emails match

I signed up on my site with my facebook account that uses the same email address as my main admin account. Ultimate facebook then associated the facebook account to the admin account I assume because it has the same email address (I was logged out with cookies deleted).

This seems to me like a bit of a security risk as if you set an admins email in your facebook then you can jump straight into the sites admin.

Is there a way to make all facebook registrations new accounts and not merge them with existing admin accounts?