Failing to build with unknown property 'indentWdith'

[securit]

I've just gone through a process of updating my app to laravel 7 and thought I would update the npm dependencies too.... bad move as I now get an error that I have 0 clue about. I'm hoping someone can point me in a sane direction.

ERROR in ./resources/sass/tailwind.scss
Module build failed (from ./node_modules/css-loader/dist/cjs.js):
ModuleBuildError: Module build failed (from ./node_modules/sass-loader/dist/cjs.js):
ValidationError: Invalid options object. Sass Loader has been initialized using an options object that does not match the API schema.
 - options has an unknown property 'indentWidth'. These properties are valid:
   object { implementation?, sassOptions?, prependData?, sourceMap?, webpackImporter? }
    at validate (/dev/atlas/node_modules/sass-loader/node_modules/schema-utils/dist/validate.js:85:11)
    at Object.loader (/dev/atlas/node_modules/sass-loader/dist/index.js:36:28)
    at runLoaders (/dev/atlas/node_modules/webpack/lib/NormalModule.js:316:20)
    at /dev/atlas/node_modules/loader-runner/lib/LoaderRunner.js:367:11
    at /dev/atlas/node_modules/loader-runner/lib/LoaderRunner.js:233:18
    at runSyncOrAsync (/dev/atlas/node_modules/loader-runner/lib/LoaderRunner.js:143:3)
    at iterateNormalLoaders (/dev/atlas/node_modules/loader-runner/lib/LoaderRunner.js:232:2)
    at /dev/atlas/node_modules/loader-runner/lib/LoaderRunner.js:205:4
    at process.nextTick (/dev/atlas/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:85:15)
    at process._tickCallback (internal/process/next_tick.js:61:11)
 @ ./resources/sass/tailwind.scss

[securit]

Ah... and then I found

let sassConfig = {
    outputStyle: mix.inProduction() ? 'compressed' : 'expanded',
    indentType:  'tab',
    indentWidth: 1
};

in my webpack.mix.js which I removed and fixed the problem. Sighs....