File Watcher: Enable Stylus Sourcemaps

I'm having trouble getting Stylus sourcemaps to work; From reading the documentation on the website, I simply need to pass in the

-m

or

--sourcemap

flag.  However, I get the following error:

cmd.exe /D /C C:/Users/User/AppData/Roaming/npm/stylus.cmd -m --use C:\Users\User\Documents\GitHub\project/node_modules/kouto-swiss app.styl --compress  C:\Users\User\AppData\Roaming\npm\node_modules\stylus\bin\stylus:587     if (err) throw err;                    ^ Error: ENOENT, stat 'C:\Users\User\Documents\GitHub\project\app\styles\stylus\-m'  Process finished with exit code 8

It appears that adding

--compress

works, without Stylus thinking I'm passing in the filedir.  But when I replace

compress

with

--sourcemap

, I get this error.

Can anyone advise on how to get sourcemaps working with PHPStorm and the Stylus plugin?