Different behaviour of unscoped between rails 3 and rails 4 - ruby-on-rails-3

Question

I have just upgraded an application from Rails 3.2.8 to Rails 4.0.2 and I've got an strange behaviour with a model that has a "default_scope" defined.
The questions is that it seems like "unscoped" (http://api.rubyonrails.org/classes/ActiveRecord/Scoping/Default/ClassMethods.html#method-i-unscoped) doesn't work in Rails 4 in the same way it used to do in Rails 3.
The problem raises when I try to chain "unscoped" with another "scope". In Rails 3 it worked fine by first removing default scope and then applying the second scope. In Rails 4, it adds the default scope always.
I have a Model defined this way:
class User < ActiveRecord::Base
......
# set a default scope to be aplied to EVERY query. to override this use "unscoped", for example: User.unscoped.all
def self.default_scope
where :active => true
end
# users that can be shown in the application
scope :not_hidden, where(:hidden => false)
.....
end
And here are some examples on how scope and unscoped are working on 3.2.8 and 4.0.2:
User.all (OK)
(3.2.8)
User.all
SELECT "users".* FROM "users" WHERE "users"."active" = 't'
(4.0.2)
User.all
SELECT "users".* FROM "users" WHERE "users"."active" = 't'
User.unscoped (OK)
(3.2.8)
User.unscoped
SELECT "users".* FROM "users"
(4.0.2)
User.unscoped
SELECT "users".* FROM "users"
User.unscoped.not_hidden (FAIL)
(3.2.8) (OK)
User.unscoped.not_hidden
SELECT "users".* FROM "users" WHERE "users"."hidden" = 'f'
(4.0.2) (FAIL)
User.unscoped.not_hidden
SELECT "users".* FROM "users" WHERE "users"."active" = 't' AND "users"."hidden" = 'f'
User.not_hidden.unscoped (OK)
(3.2.8) (OK)
User.not_hidden.unscoped
SELECT "users".* FROM "users"
(4.0.2) (OK)
User.not_hidden.unscoped
SELECT "users".* FROM "users"
Can anybody tell me if I'm missing something on how default scope and unscoped works in Rails 4?

Answer 1

That's desired behaviour (see Removing All Scoping in the guides).
Note that chaining unscoped with a scope does not work. In these
cases, it is recommended that you use the block form of unscoped:
Client.unscoped {
Client.created_before(Time.zone.now)
}

Answer 2

I have just found a solution.
I have changed not_hidden scope defintion from:
scope :not_hidden, where(:hidden => false)
To:
def self.not_hidden
where(:hidden => false)
end
And it works fine!!!!