Model generator doesn't honor --skip option

When trying to provide the --skip option to rails generate model it fails if the about to be generated migration already exists instead of just skipping it. Demonstration:

> rails -v
Rails 3.0.3
> rails new test_generator     
> cd test_generator     
> rails generate model post   

> rails generate model post --skip
      invoke  active_record
Another migration is already named create_posts: /srv/samba/share/test_generator/db/migrate/20101210161949_create_posts.rb