Preloading associations generates invalid sql for STI and has_many :through when condition added

class Role < ActiveRecord::Base
  has_many :user_roles
  has_many :users, :through => :user_roles
end

class User < BusinessObject # STI
  has_many :user_roles
  has_many :roles, :through => :user_roles
end

Role.includes(:user_roles => :user).where(:user_roles => {:role_id => '1'}).find("short name")
=> ... ON "business_objects"."id" = "user_roles"."user_id" AND "business_objects"."type" = 'User' ...

and this sql is ok however

Role.includes(:users).where(:user_roles => {:role_id => '1'}).find("short name")
=> ... ON "business_objects"."type" = 'User' ...

The most important part of the sql gets lost in the second query : ON "business_objects"."id" = "user_roles"."user_id"

This leads to totally wrong results preloaded.
where(...) in this example might not have too much sense but it is just to show simple case when such error occurs.
Preloading behaves different when there are conditions for preloaded associations.