title: Bundler is removing RUBY VERSION from Gemfile.lock
body: <p>I'm having the opposite issue to <a href="https://stackoverflow.com/questions/36316399/can-i-stop-bundler-from-adding-ruby-version-to-gemfile-lock">this one</a>. The <code>Gemfile</code> has:</p>
  
  <pre><code>source 'https://rubygems.org'
  ruby '2.3.1'
  </code></pre>
  
  <p>At the end of my <code>Gemfile.lock</code> file is:</p>
  
  <pre><code>RUBY VERSION
     ruby 2.3.1p112
  
   BUNDLED WITH
      1.12.4
  </code></pre>
  
  <p>But when I run <code>bundle install</code> is always deleting <code>RUBY VERSION</code> regardless I'm using the same as the development team's version. Even I'm using a more recent bundler version than the used to generate the original <code>Gemfile.lock</code> file:</p>
  
  <pre><code>$ bundle -v
  Bundler version 1.12.5
  $ ruby -v
  ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-linux]
  </code></pre>
  
  <p>Any ideas how can I stop this?</p>