implicit mixin with pseudo class

[tlindig]

I want include class properties of FontAwesome for a pseudo class to my-class.

.my-icon-caret-up:before { content: "\f0d8"; }

.my-class:before {
    .my-icon-caret-up:before;
}

But I got error:

Parse error: Unrecognised input
.my-class:before {        .my-icon-caret-up:before;    }

What have I to do to get it work?

I tried this on less2css.org with less 1.6.0 (current)

[seven-phases-max]

.my-icon-caret-up:before can't be used as a mixin because of its :before part.
You can just write it like this (it's even shorter syntax after all):

.my-class:before {
    content: @fa-var-caret-up;
}

Or:

.my-class {
    &:before {content: @fa-var-caret-up}
}

Or you can go an alternative way you'll find there.