Looks like c0ede38d removed an empty div which was
actually preventing some margin collapsing. Thankfully we
can force a [block formatting context][1] to also prevent [margin
collapsing][2].

[1]: https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Block_formatting_context
[2]: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Box_Model/Mastering_margin_collapsing