Error al instalar GhostJS versión 0.11.5 en Heroku

Al intentar actualizar GhostJS a la versión 0.11.5 me topé con el siguiente error:

Counting objects: 57, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (55/55), done.
Writing objects: 100% (57/57), 56.75 KiB | 0 bytes/s, done.
Total 57 (delta 35), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote: 
remote: -----> Node.js app detected
remote: 
remote: -----> Creating runtime environment
remote:        
remote:        NPM_CONFIG_LOGLEVEL=error
remote:        NPM_CONFIG_PRODUCTION=true
remote:        NODE_VERBOSE=false
remote:        NODE_ENV=production
remote:        NODE_MODULES_CACHE=true
remote: 
remote: -----> Installing binaries
remote:        engines.node (package.json):  ^4.2.0 || ^6.9.0
remote:        engines.npm (package.json):   unspecified (use default)
remote:        
remote:        Resolving node version ^4.2.0 || ^6.9.0 via semver.io...
remote:        Downloading and installing node 6.10.0...
remote:        Using default npm version: 3.10.10
remote: 
remote: -----> Restoring cache
remote:        Skipping cache restore (new runtime signature)
remote: 
remote: -----> Building dependencies
remote:        Installing node modules (package.json + shrinkwrap)
remote:        
remote:        > ghost@0.11.5 preinstall /tmp/build_6b6fff46eaea7df1627325537236afe1
remote:        > node core/server/utils/npm/preinstall.js
remote:        
remote:        ERROR: Unsupported version of Node
remote:        Ghost supports LTS Node versions: ^4.2.0 || ^6.9.0
remote:        You are currently using version: 6.10.0
remote:        This check can be overridden, see http://support.ghost.org/supported-node-versions/ for more info
remote:        
remote:        npm ERR! Linux 3.13.0-105-generic
remote:        npm ERR! argv "/tmp/build_6b6fff46eaea7df1627325537236afe1/.heroku/node/bin/node" "/tmp/build_6b6fff46eaea7df1627325537236afe1/.heroku/node/bin/npm" "install" "--unsafe-perm" "--userconfig" "/tmp/build_6b6fff46eaea7df1627325537236afe1/.npmrc"
remote:        npm ERR! node v6.10.0
remote:        npm ERR! npm  v3.10.10
remote:        npm ERR! code ELIFECYCLE
remote:        npm ERR! ghost@0.11.5 preinstall: `node core/server/utils/npm/preinstall.js`
remote:        npm ERR! Exit status 231
remote:        npm ERR!
remote:        npm ERR! Failed at the ghost@0.11.5 preinstall script 'node core/server/utils/npm/preinstall.js'.
remote:        npm ERR! Make sure you have the latest version of node.js and npm installed.
remote:        npm ERR! If you do, this is most likely a problem with the ghost package,
remote:        npm ERR! not with npm itself.
remote:        npm ERR! Tell the author that this fails on your system:
remote:        npm ERR!     node core/server/utils/npm/preinstall.js
remote:        npm ERR! You can get information on how to open an issue for this project with:
remote:        npm ERR!     npm bugs ghost
remote:        npm ERR! Or if that isn't available, you can get their info via:
remote:        npm ERR!     npm owner ls ghost
remote:        npm ERR! There is likely additional logging output above.
remote:        
remote:        npm ERR! Please include the following file with any support request:
remote:        npm ERR!     /tmp/build_6b6fff46eaea7df1627325537236afe1/npm-debug.log
remote: 
remote: -----> Build failed
remote:        
remote:        We're sorry this build is failing! You can troubleshoot common issues here:
remote:        https://devcenter.heroku.com/articles/troubleshooting-node-deploys
remote:        
remote:        If you're stuck, please submit a ticket so we can help:
remote:        https://help.heroku.com/
remote:        
remote:        Love,
remote:        Heroku
remote:        
remote:  !     Push rejected, failed to compile Node.js app.
remote: 
remote:  !     Push failed
remote: Verifying deploy...
remote: 
remote: !    Push rejected to nodenica.
remote: 
To https://git.heroku.com/nodenica.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/nodenica.git'

En el sitio de soporte de versiones de GhostJS encontraremos la solución http://support.ghost.org/supported-node-versions/

Solo debemos especificar la variable de entorno:

$ heroku config:set GHOST_NODE_VERSION_CHECK=false

De esta forma no se comprobará la versión de Node.JS en heroku y se podrá instalar GhostJS.