css3 images is not in the sourcemap

[eguneys]

I am getting this error

Module build failed: Error: "/home/ubuntu/webdev/learn/node_modules/compass-mixins/lib/compass/css3/_images.scss" is not in the SourceMap.
    at SourceMapConsumer_sourceContentFor [as sourceContentFor] (/home/ubuntu/webdev/learn/yuzbir-react/node_modules/postcss-loader/node_modules/postcss/node_modules/source-map/lib/source-map/source-map-consumer.js:677:15)
    at Input.origin (/home/ubuntu/webdev/learn/yuzbir-react/node_modules/postcss-loader/node_modules/postcss/lib/input.js:91:31)
    at Input.error (/home/ubuntu/webdev/learn/yuzbir-react/node_modules/postcss-loader/node_modules/postcss/lib/input.js:61:27)
    at Declaration.error (/home/ubuntu/webdev/learn/yuzbir-react/node_modules/postcss-loader/node_modules/postcss/lib/node.js:68:38)
    at Warning.toString (/home/ubuntu/webdev/learn/yuzbir-react/node_modules/postcss-loader/node_modules/postcss/lib/warning.js:22:30)
    at /home/ubuntu/webdev/learn/yuzbir-react/node_modules/postcss-loader/index.js:35:40
    at Array.forEach (native)
    at /home/ubuntu/webdev/learn/yuzbir-react/node_modules/postcss-loader/index.js:34:31
 @ ./app/components/OkeyStone/_OkeyStone.scss 4:14-404 13:2-17:4 14:20-410

Trying to use a mixin like this:

@mixin app($color){
@include background(linear-gradient(bottom,$color,lighten($color,10%)));
  border-bottom:solid 4px darken($color,20%);
  font-family:Lobster;
}

With webpack sass-loader.

Not sure why.