How to set column height equal to longest column in Bulma (flexbox)?

I'm using Bulma 0.4.0, though the answer may not be associated with Bulma itself.

How can I set column height equal to others? (see screenshots below)

Edit: codepen with more text that presents actual behavior: https://codepen.io/anon/pen/vmKVbx

Expected behavior:

Actual behavior:

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bulma/0.4.0/css/bulma.css" /><div class="columns"><div class="column"><p class="notification is-info">First column</p></div><div class="column"><p class="notification is-success">Second column</p></div><div class="column"><p class="notification is-warning">Third column</p></div><div class="column"><p class="notification is-danger">Fourth</p></div></div>