Require_tree unusable, @import won't cache bust

[koichirose]

Setup: my environment is currently 'local'.

Requiring tree from application.css is useless since LESS variables are scoped and won't be available in other included LESS files.

So I resorted to an application.css manifest that only requires 'app'.

app.less is the following:
@import "common/variables"
@import "common/common"
@import "home"
@import "users"
etc.

This allows me to have all my LESS variables available everywhere.

Editing "home.less" won't force refresh on the generated 'application.css'.
Removing the @import directive, refreshing the browser, then readding it solves my problem.

Is this a bug?
I couldn't find any other way to have both LESS variables and a working cache busting system. What's the best practice here?