belongs_to and includes() & joins() bug

Hi,

Calling SomeModel.includes(:users) doesn't generate INNER JOIN and throws TypeError:

class User < ActiveRecord::Base
  has_many :tunes
end

class Tune < ActiveRecord::Base
  belongs_to :user
end

class HomeController < ApplicationController
  def index
    @tunes = Tune.includes(:users).all
  end
end

Console output:

Started GET "/" for 127.0.0.1 at 2010-11-16 21:34:06 +0100
Processing by HomeController#index as HTML
Tune Load (0.6ms)  SELECT `tunes`.* FROM `tunes`
Completed   in 65ms

TypeError (can't convert nil into Integer):
app/controllers/home_controller.rb:3:in `index'

When trying to replace includes with join I'm getting this:

class HomeController < ApplicationController
  def index
    @tunes = Tune.joins(:user)
    @tunes.each do |t|
      t.user.name
    end
  end
end

Tune Load (0.8ms)  SELECT `tunes`.* FROM `tunes` INNER JOIN `users` ON `users`.`id` = `tunes`.`user_id`
User Load (0.9ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
User Load (0.3ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 2) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1
CACHE (0.0ms)  SELECT `users`.* FROM `users` WHERE (`users`.`id` = 1) LIMIT 1

I'm using Rails 3.0.2 but the problem exists in 3.0.1 too.