Libsass can't parse "font:" shorthand options that are valid for CSS

[wzup]

Looks like the library doesn't know how to parse this:

.test {
  font: normal normal 400 16px/calc(16px * 1.4) Oxygen;
}

I use webpack with node-sass. And it throws an error on 16px/calc(16px * 1.4):

ERROR in ./src/sass/globals.scss
    Module build failed: ModuleBuildError: Module build failed:
        font: normal normal 400 16px/calc(16px * 1.4) Oxygen;
                               ^
          16px/calc isn't a valid CSS value.
          in C:\Users\user\app\src\sass\globals.scss (line 15, column 29)
        at runLoaders (C:\Users\user\app\node_modules\webpack\lib\NormalModule.js:192:19)
        at C:\Users\user\app\node_modules\loader-runner\lib\LoaderRunner.js:364:11
        at C:\Users\user\app\node_modules\loader-runner\lib\LoaderRunner.js:230:18
        at context.callback (C:\Users\user\app\node_modules\loader-runner\lib\LoaderRunner.js:111:13)
        at Object.asyncSassJobQueue.push [as callback] (C:\Users\user\app\node_modules\sass-loader\lib\loader.js:57:13)
        at Object.<anonymous> (C:\Users\user\app\node_modules\async\dist\async.js:2243:31)
        at Object.callback (C:\Users\user\app\node_modules\async\dist\async.js:906:16)
        at options.error (C:\Users\user\app\node_modules\node-sass\lib\index.js:294:32)
     @ ./src/js/App.js 6:14-37
     @ ./src/js/router.js
     @ ./src/js/browser.js

At first, I thought it was sass-loader issue. Here is my initial question webpack/sass-loader#459. Guys from sass-loader said that it was libsass issue.

How to solve it?

version info:

$ node bin/node-sass --version
node-sass       4.5.3   (Wrapper)       [JavaScript]
libsass         3.5.0.beta.2    (Sass Compiler) [C/C++]