IE 11: Image doesn't scale down correctly within flexbox

IE11 seems to have some trouble with the initial value of the flex-shrink property. If you set it to zero (it is initially set to 1), it should work:

div.outer {
  width: 400px;
  display: flex;
  flex-direction: column;
  justify-content: space-around;
}
div.inner {
  flex-shrink: 0;
  width: 100%;
  border: 1px solid red;
}
img {
  width: 100%;
  height: auto;
}
<div class="outer">
  <div class="inner">
    <img src="http://placehold.it/480x360">
  </div>

  <div class="inner">
    <img src="http://placehold.it/480x360">
  </div>
</div>