Ruby on Rails

I have  a production server and a staging server and a production git branch and a staging git branch for the same repository on github. The production git branch and staging git branch are identical. I got my staging server running and during the second deploy, something unexpected started happening:

...
 ** [out :: xxx.xx.xx.xxx] Installing multi_json (1.5.0)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing activesupport (3.2.5)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing builder (3.0.4)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing activemodel (3.2.5)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing erubis (2.7.0)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing journey (1.0.4)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing rack (1.4.1)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing rack-cache (1.2)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing rack-test (0.6.2)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing hike (1.2.1)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing tilt (1.3.3)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing sprockets (2.1.3)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing actionpack (3.2.5)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing mime-types (1.19)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing polyglot (0.3.3)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing treetop (1.4.12)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing mail (2.4.4)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing actionmailer (3.2.5)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing active_record-tableless_model (0.0.1)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing arbre (1.0.1)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing sass (3.2.4)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing thor (0.16.0)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing bourbon (3.0.1)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing bcrypt-ruby (3.0.1)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing orm_adapter (0.4.0)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing rack-ssl (1.3.2)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing json (1.7.6)
 ** [out :: xxx.xx.xx.xxx]
 ** [out :: xxx.xx.xx.xxx] Installing rdoc (3.12)

It started installing gems. What I don't understand is why it did this during second deploy and not first? My staging and production gems should be identical. My deploy.rb file has this:

namespace :deploy do
  desc "Create the gemset"
  task :create_gemset do
    run "rvm #{rvm_ruby_string} --create"
  end

  desc "Install the bundle"
  task :bundle do
    run "bundle install --gemfile #{release_path}/Gemfile --without development test"
  end
end

Now the bundle install there should only be installing new gems that are added. But I didn't add any new gems during this deploy. Any idea why the capistrano task started installing the above gems?