Audio Element not accepting correct code

This page isn’t working. It keeps giving me the error:

// running test
Make sure your audio element has a closing tag.
// tests completed

…but I have a closing tag:

    <h1>Real Coding Ninjas</h1>
    <p>A sound clip of Zersiax's screen reader in action.</p>
    <audio id="zersiax" controls>
      <source src="" type="audio/mpeg" />

I did discover that if I remove the id="zersiax" code, then it works correctly.