Partial_updates feature in rails 2.1, failing to save because of validate_presence _of on other at

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:
[email protected]”, 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”