Failing example with ActiveRecord 4.1.0rc1

gistfile1.rb

# Activate the gem you are reporting the issue against.
gem 'activerecord', '4.1.0rc1'

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 do |t|

  end

  create_table :categories do |t|
  end

  create_table :post_categories do |t|
    t.integer :post_id
    t.integer :category_id

    t.boolean :prime
  end
end

class Post < ActiveRecord::Base
  has_many :post_categories
  has_many :categories, through: :post_categories

  has_many :prime_categories,
    -> {
      #includes(:post_category)
      #.references(:post_category)
      where(post_categories: { prime: true })
      .select("post_categories.id, categories.*")
    },
    through: :post_categories,
    source: :category
end

class Category < ActiveRecord::Base
  has_many :post_categories
  has_many :posts, through: :post_categories
end

class PostCategory < ActiveRecord::Base
  belongs_to :post
  belongs_to :category
end

class BugTest < Minitest::Test
  def test_association_stuff
    post = Post.create!

    category1 = Category.create!
    category2 = Category.create!

    post.post_categories.create!(
      category: category1,
      prime: true
    )

    post.post_categories.create!(
      category: category2,
      prime: false
    )

    assert_equal 2, post.categories.count
    assert_equal 1, post.prime_categories.count
  end
end