Spaces inserted inside a :not() selector when using @content

[mgol]

The following SCSS:

@mixin m() {
    .a & {
        @content;
    }
}

:not(:last-of-type) {
    top: 10px;
    @include m {
        top: 10px;
    }
}

libsass from node-sass 3.0.0-beta.4 turns into:

:not(:last-of-type) {
  top: 10px; }
  .a :not(  :last-of-type) {
    top: 10px; }

Note the two spaces before the second :last-of-type.

Latest Ruby Sass gives:

:not(:last-of-type) {
  top: 10px; }
  .a :not(:last-of-type) {
    top: 10px; }

[mgol]

Spec submitted: sass/sass-spec#297