Heroku could not find bundler error

Question

I have an old Rails 2.3.8 app using Ruby 1.8.7-p352 that I've been trying to migrate to Heroku's cedar stack. Everything works in development, deployment goes fine, but I'm getting an App Crashed error when I try to access the site.

2012-11-27T19:16:08+00:00 heroku[web.1]: Starting process with command `bundle exec thin start -p 58772 -e production`
2012-11-27T19:16:09+00:00 app[web.1]:   from /app/vendor/ruby-1.8.7/lib/ruby/site_ruby/1.8/rubygems/dependency.rb:256:in `to_spec'
2012-11-27T19:16:09+00:00 app[web.1]:   from /app/vendor/ruby-1.8.7/lib/ruby/site_ruby/1.8/rubygems.rb:1231:in `gem'
2012-11-27T19:16:09+00:00 app[web.1]: /app/vendor/ruby-1.8.7/lib/ruby/site_ruby/1.8/rubygems/dependency.rb:247:in `to_specs': Could not find bundler (>= 0) amongst [] (Gem::LoadError)
2012-11-27T19:16:09+00:00 app[web.1]:   from /app/vendor/bundle/1.8/bin/bundle:22
2012-11-27T19:16:10+00:00 heroku[web.1]: Process exited with status 1
2012-11-27T19:16:10+00:00 heroku[web.1]: State changed from starting to crashed

Is this because 1.8.7 isn't supported anymore, or is there a fix?

Edit: Adding my gemfile in response to a comment.

source :gemcutter

ruby "1.8.7"
gem "rails",   "2.3.8"
gem "bundler", "1.2.2"
gem "thin"
gem "pg"

Answer 1

See if your config vars are updated for ruby 1.8.7:

https://devcenter.heroku.com/articles/changing-ruby-version-breaks-path

Answer 2

It should work on cedar.

Are you specifying the ruby version on the Gemfile?

source "https://rubygems.org"
ruby "1.8.7"
# ...

More info about this on the Heroku docs