Meteor 1.5 - Bare app - React is undefined, unless React is used by it's name

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1

I started a bare app, added one component written as such:

import React  from 'react';
import ReactDOM from 'react-dom';

const Comp = () => (
    <div>
        Hello World.
    </div>
);

Meteor.startup(() => {
    const div = document.createElement('div');
    document.body.appendChild(div);
    ReactDOM.render(<Comp />, div);
});

I get a React is not defined error unless I put React somewhere, like this for instance:

Meteor.startup(() => {
    React;
    const div = document.createElement('div');
    document.body.appendChild(div);
    ReactDOM.render(<Comp />, div);
});