import { Theme } from "@material-ui/core/styles/createMuiTheme" import { createMuiTheme } from "@material-ui/core/styles" declare module "@material-ui/styles" { interface DefaultTheme extends MyTheme {} } declare module "@material-ui/core/styles/createMuiTheme" { interface ThemeOptions extends MyTheme {} } export interface MyTheme extends Theme { backgroundColor: string zesty: any } const theme = createMuiTheme({ backgroundColor: "red", zesty: any, }) export { theme }