Node-RED can not connect to Home Assistant over HTTPS

I have activated HTTPS for my Home Assistant (with a valid certificate) and all is working well (Node-RED is also running HTTPS, if it matters).

I have had Node-RED connected using node-red-contrib-home-assistant-websocket for a while with absolutely no problems, but now when I change the HA URL to https instead of http, it won’t connect anymore.

Both HA and NR are running in Docker and I’ve tried both the internal Docker IP and the host IP.

Does anyone know what I will have to do to make this work?