Warning message in ReactMeteorData

I’m doing a project on Meteor and I have a warning message in console.

Warning: MeteorDataContainer: React.createClass is deprecated and will be removed in version 16. Use plain JavaScript classes instead. If you're not yet ready to migrate, create-react-class is available on npm as a drop-in replacement.

But in the code I use only plain JavaScript classes to create React components (abridged version).

import { Meteor } from 'meteor/meteor';
import React, { Component } from 'react';
import { createContainer } from 'meteor/react-meteor-data';

class Header extends Component {
  render() {
    return (

export default createContainer(() => {

  return {
    user: Meteor.user()
}, Header);

How can I fix this warning? Thanks.