Problem with Bold fonts on Headings

By modifying the css file of a theme (the LYT theme), I put a custom font, and managed to switch the “fake bold” css for a proper bold font. This works great everywhere, except on headings.

I believe this is where I should specify the heading syle to use the bold font:

/headings/

h1,
.vertical-tab-content h1,
.cm-header-1,
.cm-s-obsidian .cm-inline-code.cm-header-1,
.markdown-preview-view h1 {
font-family: var(–font-header);
font-size: var(–h1);
font-weight: bold;
line-height: var(–header-line-height);

But instead, it uses the normal text font. Strangely, not even with the ligatures the font has when not used on headings.

Here’s an image where you can see the “fi” has no ligature in the heading, but does have it down in the bolden normal text:

I don’t even think it’s using the fake bold (not shown in this image), because the fake bold still preserves the ligatures of the normal font.

What am I doing wrong?

PS:
The --font-header is the same font as the normal font used everywhere else.