SVG animate fill to none results in black background

Question

I would expect this to animate to a transparent background. Any idea why it animates to black or how to fix it?

<svg>
  <rect height="100" width="100">
    <animate attributeName="fill" from="red" to="none" dur="3s" fill="freeze">
  </rect>
</svg>

Related CodePen: http://codepen.io/corysimmons/pen/Byeoyw?editors=100

Answer 1

none isn't valid. transparent works as expected.