nuxt 2: postcss-preset-env: Unknown feature: "customProperties", did you mean: "custom-properties"

I've recently had my nuxt project not compiling anymore:

WARN  Compiled with 1 warnings

WARN  in /build/components/nuxt-error.vue?vue&type=style&index=0&id=2b6db950&lang=css&

Module Warning (from ./node_modules/postcss-loader/dist/cjs.js):
Warning

(1:1) postcss-preset-env: Unknown feature: "customProperties", did you mean: "custom-properties"

@ ./node_modules/vue-style-loader??ref--3-oneOf-1-0!./node_modules/css-loader/dist/cjs.js??ref--3-oneOf-1-1!./node_modules/vue-loader/lib/loaders/stylePostLoader.js!./node_modules/postcss-loader/dist/cjs.js??ref--3-oneOf-1-2!./node_modules/vue-loader/lib??vue-loader-options!/build/components/nuxt-error.vue?vue&type=style&index=0&id=2b6db950&lang=css& 4:14-352 15:3-20:5 16:22-360
@ /build/components/nuxt-error.vue?vue&type=style&index=0&id=2b6db950&lang=css&
@ /build/components/nuxt-error.vue
@ /build/index.js
@ /build/client.js
@ multi ./node_modules/eventsource-polyfill/dist/browserify-eventsource.js (webpack)-hot-middleware/client.js?reload=true&timeout=30000&ansiColors=&overlayStyles=&path=%2Fmon-espace%2F__webpack_hmr%2Fclient&name=client /build/client.js


ERROR  Failed to compile with 1 errors

This relative module was not found:

* ./index.vue?vue&type=style&index=0&id=a00a9554&scoped=true&lang=scss& in ./pages/my_path/_slug/index.vue

Anyone has this error? I have been investigating quite a lot, trying to upgrade dependencies, without success.

Here's my current config:

    "nuxt": "^2.16.2",
    "sass": "^1.59.3",
    "vue": "^2.7.14"

Ok my bad, I had this config remaining in my nuxt.config.js file:

  build: {
    postcss: {
      preset: {
        features: {
          customProperties: false,
        }
      }
    },
  },

which made it fail when I upgraded my nuxt version.

Of course it was not in the main config file but in some sub-imported file otherwise I would have seen it quicker but whatever!