PhantomJSのbuildpackは既に1.9.8に更新されています。
stomita/heroku-buildpack-phantomjs
ので、git対象のファイルを何か更新して、herokuにpushしてやればOKです（ファイル更新無しにherokuの更新は出来ないのだろうか…）。
ログはこんな感じ。
$ git push heroku master Fetching repository, done. Counting objects: 5, done. Delta compression using up to 4 threads. Compressing objects: 100% (3/3), done. Writing objects: 100% (3/3), 384 bytes | 0 bytes/s, done. Total 3 (delta 2), reused 0 (delta 0) -----> Fetching custom git buildpack... done -----> Multipack app detected =====> Downloading Buildpack: https://github.com/stomita/heroku-buildpack-phantomjs.git =====> Detected Framework: PhantomJS -----> Fetching PhantomJS 1.9.8 binaries at https://bitbucket.org/ariya/phantomjs/downloads/phantomjs-1.9.8-linux-x86_64.tar.bz2 -----> Extracting PhantomJS 1.9.8 binaries to /tmp/build_ced593d0c5dad7374e020f42bb141e6e/vendor/phantomjs -----> exporting PATH and LIBRARY_PATH =====> Downloading Buildpack: https://github.com/heroku/heroku-buildpack-ruby.git =====> Detected Framework: Ruby -----> Compiling Ruby/Rack -----> Using Ruby version: ruby-1.9.3 -----> Installing dependencies using 1.6.3 Ruby version change detected. Clearing bundler cache. Old: ruby 1.9.3p547 (2014-05-14 revision 45962) [x86_64-linux] New: ruby 1.9.3p551 (2014-11-13 revision 48407) [x86_64-linux] Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment Fetching gem metadata from https://rubygems.org/....... Fetching additional metadata from https://rubygems.org/.. ：（中略） Installing selenium-webdriver 2.41.0 Installing watir-webdriver 0.6.9 Your bundle is complete! Gems in the groups development and test were not installed. It was installed into ./vendor/bundle Bundle completed (39.86s) Cleaning up the bundler cache. Using release configuration from last framework (Ruby). -----> Discovering process types Procfile declares types -> cron Default types for Multipack -> console, rake, web -----> Compressing... done, 40.7MB -----> Launching... done, v30 https://helloxxx.herokuapp.com/ deployed to Heroku To git@heroku.com:helloxxx.git b3d0ec9..8c60e70 master -> master
