How to share JSS class across multiple components located in multiple files?

I am using React with Material UI and am refactoring one of my components now. My original component looks something like this:

// All the import statements here

const styles = theme => ({
  container: {
    margin: 'auto',
    maxWidth: '1200px',
    background: theme.palette.primary.main
    // More styles here
  },
});

const Component = ({ classes }) => (
  <div>
    <div className={classes.container}>
      {/* Some content */}
    </div>
    <div className={classes.container}>
      {/* Some content */}
    </div>
  </div>
);

export default withStyles(styles)(Component);

But after refactoring the component I need to access the 'container' class in two different components. The only approach I could come up with was creating a new file in my root called sharedStyles.js, which I then import in both of those components and extend its style object like this:

File: sharedStyles.js

export default theme => ({
  container: {
    margin: 'auto',
    maxWidth: '1200px',
    background: theme.palette.primary.main
    // Some more styles
  },
});

File: NewComponent.js

// All the import statements here - including the sharedStyles.js

const styles = theme => ({
  ...sharedStyles(theme),
  // Some more styles
});

const NewComponent = ({ classes }) => (
  <div className={classes.container}>
    {/* Some content */}
  </div>
);

export default withStyles(styles)(NewComponent);

File: RefactoredComponent.js

// All the import statements here - including the sharedStyles.js 
// and NewComponent.js

const styles = theme => ({
  ...sharedStyles(theme),
  // Some more styles
});

const RefactoredComponent = ({ classes }) => (
  <div>
    <NewComponent />
    <div className={classes.container}>
      {/* Some content */}
    </div>
  </div>
);

export default withStyles(styles)(RefactoredComponent);

Even though this approach works, I don't really like it. So my question is: Is there a better way how to share one JSS class across multiple components located in multiple files?.