Property 'X' does not exist on type 'Record<never, string>'

Hello

I’m trying to Migrate from MUI v4 to MUI v5, I’m following those guides:

https://mui.com/material-ui/migration/migration-v4/ https://mui.com/material-ui/migration/migrating-from-jss/#2-use-tss-react

Currently I have issue regarding classes, On some components the classes type I’m getting is Record<never, string> and when I try to use it, I’m getting Property ‘X’ does not exist on type ‘Record<never, string>’,

and on other components the classes type is correct.

App.js

import { ThemeProvider } from '@mui/material';
import theme from 'theme';
import CssBaseline from '@mui/material/CssBaseline';
import { Snackbar } from 'utils/snackbar';
import NoConnection from 'utils/NoConnection';
import MainRoutes from 'routes';
import { Provider } from 'react-redux';
import store from 'redux/store';
import { LocalizationProvider } from '@mui/x-date-pickers';
import { AdapterDateFns } from '@mui/x-date-pickers/AdapterDateFns';
import createCache from '@emotion/cache';
import { CacheProvider } from '@emotion/react';
import '@fontsource/roboto/300.css';
import '@fontsource/roboto/400.css';
import '@fontsource/roboto/500.css';
import '@fontsource/roboto/700.css';


export const muiCache = createCache({
  key: 'mui',
  prepend: true,
});

function App() {
  return (
    <Provider store={store}>
      <CacheProvider value={muiCache}>
        <ThemeProvider theme={theme}>
          <LocalizationProvider dateAdapter={AdapterDateFns}>
            <Snackbar>
              <CssBaseline />
              <NoConnection />
              <MainRoutes />
            </Snackbar>
          </LocalizationProvider>
        </ThemeProvider>
      </CacheProvider>
    </Provider>
  );
}

export default App;

[JeanGautierSherpas]

Hey, just passing by ! Did you use a custom property transition, in you’re MUI theme ?

[Mohammed-Mounir]

Done

BTW do you know a better guide for mui 5 migration?