<!DOCTYPE html>
<link href="resources/flexbox.css" rel="stylesheet">

<p>You should see no red.</p>

<div class="flexbox column align-items-stretch" style="background-color: red;">
  <div style="background-color: green; height: 20px;"></div>
  <div style="writing-mode: vertical-lr; background-color: green; height: 20px;"></div>
</div>