@function next-breakpoint($breakpoint) {
    @if map-has-key($mix-mq-breakpoints, $breakpoint) {
        $last: length($mix-mq-breakpoints);
        $current: index(map-keys($mix-mq-breakpoints), $breakpoint);

        @if ($current == $last) {
            @return null;
        }

        @return nth(map-keys($mix-mq-breakpoints), $current + 1);

    } @else {
        @return null;
    }
}