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.

Answer 2

None of these worked for me, but I finally figured it out:

spring stop 

I had a Rails 4 project that uses something called Spring to keep a Rails environment running in the background, for speed.

I had started Spring with Ruby 2.1.1 but then I upgraded to 2.1.2 (in Gemfile and .ruby-version). My theory is that Spring kept on running on 2.1.1 and so caused this error.