Support for Node.js 4.x will be removed in the first release of the Ruby buildpack after 2018-06-07.

The Node.js Release Working Group ended support for Node.js 4.x on 2018-04-30 [1][2]. We are giving users a 30 day notice before support for Node.js 4.x is officially removed from the Ruby buildpack. We recommend migrating any applications using release 4.x to LTS release 6.x

Scott Sisil

CF Buildpacks PM

[1] https://github.com/nodejs/Release
[2] https://medium.com/the-node-js-collection/april-2018-release-updates-from-the-node-js-project-71687e1f7742