wrong class when using scope together with sti

Using rails beta3 and ruby 1.9.2-head.

class User < ActiveRecord::Base
scope :active, where(:active => true) end

class NormalUser < User
end

User.active.first.class
=> User

NormalUser.first.class
=> NormalUser

NormalUser.active.first.class
=> User (should be NormalUser!!!)