Diff of wiki content is not showing up

1/ Create a one line page
2/ Change that line
3/ Go to changes and perform a diff between version 1.1 and 1.2

No content is showing up in the diff:

This is the html of the diff. Nothing there.
<h2>Content changes</h2>
<div class="diff-container">
<table>
</table>
</div>