HELP: rake db:migrate -> uninitialized constant

Why is this error happening? I am using Rails 1.2.3.

./script/generate model MyNewModel
      exists app/models/
      exists test/unit/
      exists test/fixtures/
      create app/models/my_new_model.rb
      create test/unit/my_new_model_test.rb
      create test/fixtures/my_new_models.yml
      exists db/migrate
      create db/migrate/010_my_new_models.rb
% rake db:migrate
(in /tmp)
rake aborted!
uninitialized constant MyNewModel

(See full trace by running task with --trace)

% rails --version
Rails 1.2.3

Try re-running the migration with the --trace option. It will dump a
strack trace along with the error message showing you (or us if you
post the output here) exactly where the migration is choking.