postcss-nested: empty classes stripped out break postcss-modules

Hi, I have this CSS:

.Foo
  &__bar
    color: red

I want to compile it and use postcss-modules to get the classes out of it, it should output:

{
 Foo: 'hash',
 Foo__bar: 'hash',
}

The problem is that this plugin is going to output only:

.Foo__bar { color: red; }

and then postcss-modules isn’t able to extract .Foo.

You can reproduce the problem here: https://runkit.com/fezvrasta/59775c35542cda0012cc20ef

Ideas?