blongs_to unscope not respected in includes - rails 4.2.3

rails-issue-20633.rb rails-4.2.3.rc1-unscope-bug.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  # Activate the gem you are reporting the issue against.
  gem 'activerecord', '4.2.3'
  gem 'sqlite3'
end

require 'active_record'
require 'minitest/autorun'
require 'logger'

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.string :title
    t.datetime :deleted_at
  end

  create_table :comments, force: true do |t|
    t.integer :post_id
  end
end

class Post < ActiveRecord::Base
  has_many :comments

  default_scope { where deleted_at: nil }
end

class Comment < ActiveRecord::Base
  belongs_to :post, -> { unscope(where: :deleted_at) }

  scope :sorted_post_title, -> {
    includes(:post).order('posts.title ASC')
  }

  def post_title
    post.title
  end
end

class BugTest < Minitest::Test
  def test_association_stuff
    post1 = Post.create! title: 'Post 1'
    post2 = Post.create! title: 'Post 2'

    comment1 = Comment.create! post: post1
    comment2 = Comment.create! post: post2

    post1.deleted_at = DateTime.now
    post1.save!

    assert_equal 1, Post.count

    assert_equal ['Post 1', 'Post 2'], Comment.sorted_post_title.map(&:post_title)
  end
end