That's a Sass issue, and should be fixed in Sass 3.3 (currently in alpha). In order to set a fallback class, Susy has to use the Sass parent selector (&
) — but that selector fails when there is no parent. We've been tracking the issue on GitHub, and you can find a few work-arounds in that thread. Basically, if you use the fallback class (before Sass 3.3), you have to nest at-breakpoint
inside another selector. In most cases (including yours) that's a simple as moving the mixin inside your existing selectors:
.l-header,
.l-main,
.l-footer,
.l-region--navigation {
@include at-breakpoint($desk) {
@include set-container-width;
}
}