Build error: Gatsby 3 and Gatsby-material-ui v3 error in lazy result.

[mariovde]

Hi

Just updated to gatsby 3 and upgraded gatsby material ui to v3.
When running the build, I get this error:

gatsby-plugin-material-ui/node_modules/autoprefixer/node_modules/postcss/lib/
lazy-result.js: Property name expected type of string but got null

gatsby-config.js:
...

// Material ui
        // Material UI injection
        {
            resolve: "gatsby-plugin-material-ui",
            options: {
                stylesProvider: {
                    injectFirst: true,
                },
            },
        },
...

already tried this (found at other issue)

cd node_modules/gatsby-plugin-material-ui
yarn install --frozen-lockfile
yarn run build

but didn't work

any ideas or can I provide you with more information?