Custom properties declared on :host not being applied

[tuespetre]

I've got several elements within a <template> that need to make use of a couple/few custom properties (for coloring, size, etc.) and I've got the defaults for those properties declared on :host:

:host {
    --my-custom-prop: #555;
}

.some-descendant-of-host {
    background-color: var(--my-custom-prop);
}

.another-descendant-of-host {
    background-color: var(--my-custom-prop);
}

Using IE11, the generated style in head has blank values for the background-color properties.

[tuespetre]

Heads up, I am working on this right now.