I installed all of my gems using bundler via the Gemfile. I thought (mistakenly) that if I deleted a gem from my Gemfile and ran \'bundle install\' that the deleted gems would b
I seemed to solve this by manually removing the unicorn gem via bundler ("sudo bundler exec gem uninstall unicorn"), then rebundling ("sudo bundle install").
Not sure why it happened though, although the above fix does seem to work.