Libsass: @mixin inside @media (compiles with Sass v3.4.21)

[glen-84]

@media all {
  @mixin foo() {}
}

Ruby Sass

LibSass

Error: Mixins may not be defined within control directives or other mixins.
        on line 75 of test.scss
>>   @mixin foo() {}
   --^

Spec added https://github.com/sass/sass-spec/pull/911

[xzyfer]

Thanks @glen-84 I've confirmed this is a bug with defining mixins within @media. The work around for now is moving the @mixin outside the @media.