Flexbox 'space-between' not working in IE11

Question

I'm trying to align content to top and bottom with flexbox. It seems like it should be simple but I can't get it to work in IE11. Any ideas/suggestions?

.wrap {
  display: flex;
  flex-direction: column;
  min-height:100vh;
  justify-content: space-between;
}

<div class="wrap">
  <div class="top">Top</div>
  <div class="bottom">Bottom</div>
</div>