HerokuでBuild failedと返される非エンジニアです。

Herokuでgit push heroku masterする

-----> Ruby app detected
-----> Compiling Ruby/Rails
-----> Using Ruby version: ruby-2.0.0
-----> Installing dependencies using 1.6.3
Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
You are trying to install in deployment mode after changing
your Gemfile. Run bundle install elsewhere and add the
updated Gemfile.lock to version control.
You have added to the Gemfile:
* pg
* therubyracer
Bundler Output: You are trying to install in deployment mode after changing
your Gemfile. Run bundle install elsewhere and add the
updated Gemfile.lock to version control.
You have added to the Gemfile:
* pg
* therubyracer
!
! Failed to install gems via Bundler.
!
! Push rejected, failed to compile Ruby app```

しかしページは表示される

Heroku | Welcome to your new app!
https://yourapp0915.herokuapp.com/

Gemfileを書き換えるといっても、therubyracerは先頭の#を消してるし、あと何をすれば良いのやら・・。頭を悩ませています。