Scss suffixes is not working

[Ruan]

When I run the command: bundle exec rake assets:precompile.

I receive the following error: Sass::SyntaxError: Invalid CSS after "&-": expected number or function, was "-another {".

My code:

.example {
    &-another {
        color: red;
    }
}

I'm using version 6 when I receive this error. Version 5.1 compile WITHOUT errors. Probably some bug between these two versions.