Ruby 2.4.0-preview2 now available on Heroku

Change effective on 22 September 2016

Ruby v2.4.0 preview2 is now available on Heroku. To run your app using this preview version of Ruby, add the following ruby directive to your Gemfile:

ruby "2.4.0"

Note: This version of Ruby is not suitable for production applications. However, it can be used to test that your application is ready for December release of Ruby 2.4.0 and to provide feedback to the Ruby core team.