Not enought escaping in calc()

[t0rum]

Less is known to behave wierd on styles like

.box{
    width: calc(100%-30px);
}

wich results in something like

.box{
    width: calc(70%);
}

as described here:
https://stackoverflow.com/questions/11972084/less-aggressive-compilation-with-css3-calc

so, additional escaping is required to preserve original functionality, e.g.

.box{
    width: calc( ~"100%-30px");
}