Rails - Jul 2009 - accepts_nested_attributes_for and has_one

Hi all, I''m seeing some unexpected behaviour in a nested model and
I''m
not sure if it''s a bug or if I''m doing something wrong.  When
assigning nested attributes, the associated object gets replaced with
a new record.

Example code:

class Car < ActiveRecord::Base
  belongs_to :driver
end

class Car < ActiveRecord::Base
  belongs_to :driver
end

Here''s some console output:
(pastie version: http://pastie.org/538782)
>> d = Driver.create :name => "Homer", :age => 40
=> #<Driver id: 1, name: "Homer", age: 40, created_at:
"2009-07-08
16:54:44", updated_at: "2009-07-08
16:54:44">
>> d.create_car :make => "Porshce", :model =>
"911"
=> #<Car id: 1, driver_id: 1, make: "Porshce", model:
"911",
created_at: "2009-07-08 16:55:26", updated_at: "2009-07-08
16:55:26">
>> d.new_record?
=> false
>> d.car.new_record?
=> false
>> d.car.id
=> 1
>> d.car.attributes
=> {"model"=>"911", "driver_id"=>1,
"created_at"=>Wed Jul 08 16:55:26
UTC 2009, "updated_at"=>Wed Jul 08 16:55:26 UTC 2009,
"id"=>1,
"make"=>"Porshce"}
>> attrs = {:car_attributes => {:model => "Boxster"}}
=>
{:car_attributes=>{:model=>"Boxster"}}
>> d.attributes = attrs
=>
{:car_attributes=>{:model=>"Boxster"}}
>> d.car.attributes
=> {"model"=>"Boxster", "driver_id"=>1,
"created_at"=>nil,
"updated_at"=>nil,
"make"=>nil}
>> d.car.id
=> nil
>> d.car.new_record?
=> true

any ideas?