Can't extend a nested class (concatenated selector)

Heya guys.

I have found an annoying issue, which is pretty basic use of two mechanics:
I cant extend a class i generate by nesting it using "& {}"

Heres my example:

.box {
    padding: @base-spacing;

    &--large {
        padding: @large-spacing;
    }
}

.foo {
    &:extend(.box--large);
}

Expected result:

.box {
    padding: 24px;
}

.box--large,
.foo {
        padding: 48px;
}

What actually happens:

.box {
    padding: 24px;
}

.box--large {
    padding: 48px;
}

Imo this is very basic use of two mechanics, and it's not like its generated by some kind of wizard looping mixin.
Looking forward to have this fixed :-)

Kind regards, Dennis

Reproduce the nested selector and extend example from the issue in the Less compiler, then compare the generated CSS with the expected output. Trace the selector-extension entry point that handles the concatenated .box--large selector. Done means the output includes .foo alongside .box--large for the nested class.