Font mapping fails when using line-height

[MuhKuh7]

In my Avalonia Desktop app I am using font mapping

if (appl.TryGetResource("FigtreeFont", appl.ActualThemeVariant, out var fontRes) && fontRes != null)
{
	htmlPanel.Container.AddFontFamily((FontFamily)fontRes);
	htmlPanel.Container.AddFontFamilyMapping("monospace", "Figtree");
}

with the following CSS:
* { font-family: monospace; }

This works, unless I add line-height:
* { font-family: monospace; line-height: 1.5; }

The line height will change according to the given value, but the font reverts to monospace.