I would prefer this line is `gem "rails", "~> 4.0.1"` And actually it looks like the latest release is 4.0.3 https://rubygems.org/gems/rails so `gem "rails", "~> 4.0.3"` Using the `~>` just makes it easier to upgrade in the future  because you can run `bundle update rails` and it will update without needing to edit the Gemfile.