rake db:migrate gives deprecation warning

[bill-auger]

bundle exec rake db:migrate RAILS_ENV=test
== 20111119180638 CreateMovies: migrating =====================================
-- create_table(:movies)
DEPRECATION WARNING: `#timestamps` was called without specifying an option for `null`. In Rails 5, this behavior will change to `null: false`. You should manually specify `null: true` to prevent the behavior of your existing migrations from changing. (called from block in up at /media/bill/9577fb3c-bcf8-4db2-af8c-35c54e354879/sync/code/moocs/saas/HW-ACCEPTANCE-UNIT-TEST-CYCLE/git/hw-acceptance-unit-test-cycle/rottenpotatoes/db/migrate/20111119180638_create_movies.rb:10)