Operation on an invalid type

On compiling Less after migrating it from v2 to v3. It throws following error on less v3.9.0:

Operation on an invalid type
      in /home/nilesh/Desktop/plone-react/node_modules/semantic-ui-less/definitions/elements/container.less (line 143, column 0)

I was wondering correct way to use calc() function? -cc @Albert , Victor
calc(~"@var1 + @var2") didn't work so far
They're each different for different less version release.
Downgrading less to v3.0.4 fixes this, but errored on production builds.
Here's the snippet:

@tabletGridWidth: ~"calc("@tabletWidth~" + "@gridGutterWidth~")";
@computerGridWidth: ~"calc("@computerWidth~" + "@gridGutterWidth~")";
@largeMonitorGridWidth: ~"calc("@largeMonitorWidth~" + "@gridGutterWidth~")";