IE issue with svg viewBox without specific height

Question

This is the code :

<svg viewBox="0 0 70 35" preserveAspectRatio="xMidYMid meet" class="canvas">...</svg>

and this is the css :

.canvas {
width: 70px;
}

The problem is that the aspect ratio is not preserved in IE (11, 10), although it works in Chrome.

Any idea on how to solve this issue in IE ?