figaro: Unable to run 'rake figaro:heroku' task

Since I’m using the heroku toolbelt instead of the gem, I was originally getting the following error:

~ $ rake figaro:heroku
There was an error in your Gemfile, and Bundler cannot continue.
There was an error in your Gemfile, and Bundler cannot continue.

After installing the gem (ignoring deprecation warnings):

~ $ rake figaro:heroku
production
rake aborted!
can't convert true into String

config/application.yml Note: This is working in development

# Application Configuration Variables
TWITTER_CONSUMER_KEY: 'XXXXXXXXXXX'
TWITTER_CONSUMER_SECRET: 'XXXXXXXXXXXXXXXX'
development:
  FACEBOOK_APP_ID: 'XXXXXXXXXXXX'
  FACEBOOK_APP_SECRET: 'XXXXXXXXXXXXXXXXXXXX'
production:
  FACEBOOK_APP_ID: 'XXXXXXXXXXXX'
  FACEBOOK_APP_SECRET: 'XXXXXXXXXXXXXXXXXXXX'

The error with trace:

~ $ rake figaro:heroku --trace
** Invoke figaro:heroku (first_time)
** Invoke environment (first_time)
** Invoke disable_rails_admin_initializer (first_time)
** Execute disable_rails_admin_initializer
** Execute environment
** Execute figaro:heroku
production
rake aborted!
can't convert true into String
/Users/emily/.rvm/gems/ruby-1.9.3-p194@ehip_news/gems/railties-3.2.8/lib/rails.rb:86:in `initialize'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@ehip_news/gems/railties-3.2.8/lib/rails.rb:86:in `new'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@ehip_news/gems/railties-3.2.8/lib/rails.rb:86:in `env='
/Users/emily/.rvm/gems/ruby-1.9.3-p194@ehip_news/gems/figaro-0.5.0/lib/figaro/tasks.rake:6:in `block (2 levels) in <top (required)>'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:205:in `call'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:205:in `block in execute'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:200:in `each'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:200:in `execute'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:158:in `block in invoke_with_call_chain'
/Users/emily/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:144:in `invoke'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:116:in `invoke_task'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `block (2 levels) in top_level'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `each'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `block in top_level'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:88:in `top_level'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:66:in `block in run'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:63:in `run'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/bin/rake:33:in `<top (required)>'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/bin/rake:19:in `load'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@global/bin/rake:19:in `<main>'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@ehip_news/bin/ruby_noexec_wrapper:14:in `eval'
/Users/emily/.rvm/gems/ruby-1.9.3-p194@ehip_news/bin/ruby_noexec_wrapper:14:in `<main>'
Tasks: TOP => figaro:heroku