title: "Invalid multibyte char (US-ASCII)" error for ä, ü, ö, ß which are Ascii!
body: <p>My application needs to handle some international characters, namely ä, ü, ö and ß, which are still ascii.</p>
  
  <p>When I tested the behavior of ruby when dealing with these chars, I got this error:</p>
  
  <pre><code>test.rb:1: invalid multibyte char (US-ASCII)
  test.rb:1: invalid multibyte char (US-ASCII)
  </code></pre>
  
  <p>for this code:</p>
  
  <pre><code>puts "i like my chars: ä, ü, ö and ß!"
  </code></pre>
  
  <p>But the strange thing is: When using the Interactive Ruby Shell, I get no error!</p>
  
  <p><strong>EDIT: In my application, I'm retrieving the data from an external api. The above code is just an example!</strong></p>