Evolution: Spell check in Markdown as HTML

If the setting “Composer Preferences > General > Default Behavior > Format messages in” is set to “Markdown as HTML,” when I start writing an email, there is no spell check.
If I set that option to “HTML”, there is spell check.
But most weirdly, if I set that option to “HTML” but inside a new message I change it to “Markdown as HTML,” there is spell check.

Is there a way to have spell check enabled when the default option is “Markdown as HTML”?

I’m using Evolution 3.46.4-2 in Debian.