(node:3208) UnhandledPromiseRejectionWarning

[speciale]

Hello

This is my file

{
	"in": "in.css",
	"out": "out.css",
	"sourcemaps": {
        "map": {
            "inline": false
        }
    },
	"autoprefixer": true,
	"filters": true,
	"rem": true,
	"pseudoElements": true,
	"opacity": true,
	"import": true,
	"minifier": true,
	"mqpacker": true,
	"next": true
}

And this is what I get

(node:3191) UnhandledPromiseRejectionWarning: TypeError [ERR_INVALID_ARG_TYPE]: The "data" argument must be of type string or an instance of Buffer, TypedArray, or DataView. Received an instance of SourceMapGenerator
at Object.writeFileSync (fs.js:1460:5)
at /usr/local/lib/node_modules/pleeease-cli/lib/cli.js:192:16
at processTicksAndRejections (internal/process/task_queues.js:93:5)
(Use node --trace-warnings ... to show where the warning was created)
(node:3191) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag --unhandled-rejections=strict (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:3191) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Seems to be only a warning for the sourcemaps. Writes the output (out.css) but fails to write the source map

Thanks in advance