How to fix "Your Ruby version is 1.9.3, but your Gemfile specified 2.0.0"

Question

I created a Ruby project, but when running bundle update and bundle install it returns an error:

Your Ruby version is 1.9.3, but your Gemfile specified 2.0.0

An image of it is: http://i.imgur.com/dZMhI11.png?1

My gemfile is:

ruby '2.0.0'
#ruby-gemset=railstutorial_rails_4_0

gem 'rails', '4.0.0'

group :development do
    gem 'sqlite3', '1.3.8'
end

gem 'sass-rails', '4.0.0'
gem 'uglifier', '2.1.1'
gem 'coffee-rails', '4.0.0'
gem 'jquery-rails', '3.0.4'
gem 'turbolinks', '1.1.1'
gem 'jbuilder', '1.0.2'

group :doc do
    gem 'sdoc', '0.3.20', require: false
end

Answer 1

I've noticed this happening when I've tried to bundle install with a fresh RVM gemset that didn't yet include bundler (as it fell back on the system bundler install which referenced the system ruby).

Running gem install bundler fixed for me.