Dojo build with xstyle, issue with Font Awasome with ASCII conversion

Question

I am using xstyle plugin into my dojo build process.

All css is concatenated and minified, but I have notice that it translate ASCII reference like this

#test {
  content:  "\f000"
}

to this:

#test {
  content: "";
}

I need instead to keep the same ASCII value as content: "\f000" in the final CSS style.

In my specific case I am building a dojo flat theme which include Font Awasome.

How to achieve this?