Adding some URL failed but should have worked

On master I tried adding https://lesjours.fr/ and got:

Error downloading https://lesjours.fr/https://lesjours.fr/rss.xml, code 404

The page contains

<link rel="alternate" type="application/rss+xml" href="https://lesjours.fr/rss.xml" />

Adding https://lesjours.fr/rss.xml works.