Could not find gem 'rails x86-mingw32'

I'm doing the Rails Tutorial by Michael Hartl and I ran into this problem when trying to run the rails server.

This is is my gem file

gem 'rails', '4.1.5'

gem 'sqlite3'

gem 'sass-rails', '~> 4.0.3'

gem 'uglifier', '>= 1.3.0

gem 'coffee-rails', '~> 4.0.0'

gem 'jquery-rails'

gem 'turbolinks'

gem 'jbuilder', '~> 2.0'

gem 'sdoc', '~> 0.4.0',

gem 'tzinfo-data', platforms: [:mingw, :mswin]