partial_updates feature in rails 2.1, failing to save because of validate_presence _of on other attributes in the table

I am trying to use the new partial_updates feature in rails 2.1,
http://dev.rubyonrails.org/changeset/9157
but it is failing by trying to use all validations in the model
instead of just the changed attributes. The model works as I can
successfully .save(false) but if I try a regular .save I get an error
saying that it could not save because of validations problems. I want
to use this to get around the challenges of saving a part of a wide
table without resorting to the validation_scenarios plugin.

Any ideas on how I can fix this?

Black-Mac:turbocis89 Charles$ script/console
Loading development environment (Rails 2.0.991)

Spec.partial_updates

=> true

User.partial_updates

=> true

@user = User.find_by_screen_name('vince888')

=> #<User id: 1, screen_name: "vince888", password: "vince888", email:
"vince@vince888.com", created_at: "2008-05-15 12:35:12", updated_at:
"2008-05-15 13:03:38", authorization_token: nil>

@user.spec.city_of_birth

=> "Wichita"

@user.spec.city_of_birth = 'Charleston'

=> "Charleston"

@user.spec.changes

=> {"city_of_birth"=>["Wichita", "Charleston"]}

@user.spec.save

=> false ### in the application this
is failing because of other unrelated attributes not passing
validations.

@user.spec.save(false)

=> true

@user.spec.changes

=> {}

@user.spec.city_of_birth

=> "Charleston"