Error deploying jekyll to heroku?

I'm trying to deploy a jekyll app to heroku... it runs locally with no issues.

Here's the heroku log

2012-06-21T18:02:26+00:00 heroku[web.1]: State changed from crashed to created
2012-06-21T18:02:26+00:00 heroku[web.1]: State changed from created to starting
2012-06-21T18:02:28+00:00 heroku[web.1]: Starting process with command `jekyll --server 37139`
2012-06-21T18:02:29+00:00 app[web.1]: bash: jekyll: command not found
2012-06-21T18:02:30+00:00 heroku[web.1]: Process exited with status 127
2012-06-21T18:02:30+00:00 heroku[web.1]: State changed from starting to crashed
2012-06-21T18:02:31+00:00 heroku[router]: Error H10 (App crashed) -> GET furious-dusk-3604.herokuapp.com/ dyno= queue= wait= service= status=503 bytes=
2012-06-21T18:02:32+00:00 heroku[router]: Error H10 (App crashed) -> GET furious-dusk-3604.herokuapp.com/favicon.ico dyno= queue= wait= service= status=503 bytes=
2012-06-21T18:02:36+00:00 heroku[router]: Error H16 (Redirect to herokuapp.com) -> GET furious-dusk-3604.herokuapp.com/ dyno= queue= wait= service= status=301 bytes=

The line

2012-06-21T18:02:29+00:00 app[web.1]: bash: jekyll: command not found

caught my attention, but I don't really know what could be the problem here. In my Gemfile I did specify

gem 'jekyll'

Cheers!