Using @supports in combination with %placeholders can leave placeholder names in compiled css file

[mkstix6]

%hoverbrighter {
    &:hover,
    &:focus {
        opacity: .8;

        @supports (filter: brightness(120%)) {
            filter: brightness(120%);
        }
    }
}

.productportal-link {
    @extend %hoverbrighter;
}

--- can compile to ---

.productportal-link:hover, .productportal-link:focus {
  opacity: .8;
}

@supports (filter: brightness(120%)) {
  %hoverbrighter:hover, .productportal-link:hover, %hoverbrighter:focus, .productportal-link:focus {
    filter: brightness(120%);
  }
}

I don't think the %hoverbrighter should be there in the compiled result.

On SassMeister the result is as I would expect http://www.sassmeister.com/gist/cd5494dd2f57ccf90b48a87c862c8f6f.

[mgreter]

This seems to be fixed on latest master.