i18n cookbook using JIT: System is not defined error

[MeMeMax]

Following the i18n cookbook i get System is not defined.
Im using latest Angular CLI.
The issue comes up in the <script> tag which has to be included to the index.html.

<script>
  // Get the locale id somehow
  document.locale = 'es';

  // Map to the text plugin
  System.config({
    map: {
      text: 'systemjs-text-plugin.js'
    }
  });

  // Launch the app
  System.import('main.js').catch(function(err){ console.error(err); });
</script>

I loaded system.js as a dependency with npm install systemjs --save and included it to the scripts part in my angular-cli.json. But there is a timing issue as the <script> tag above is evaluated first and after that the dependencies from the angular-cli.json are loaded. So System is not defined.