HTTP Strict Transport Security (HSTS) is not persistent

When e.g. visiting https://hsts.badssl.com/ in Chrome/Chromium, restarting it, and then visiting http://hsts.badssl.com/ the request automatically gets upgraded as expected.

When doing the same with QtWebEngine, requests in the same instance do get upgraded, but as soon as it's restarted and http://hsts.badssl.com/ is opened again, no upgrade is done (a red page appears).