Modal.setAppElement() has no effect

[evoyy]

The modal is always mounted to document.body, whether setAppElement() is called or not:

  componentDidMount: function() {
    this.node = document.createElement('div');
    this.node.className = 'ReactModalPortal';
    document.body.appendChild(this.node);
    this.renderPortal(this.props);
  },

https://github.com/rackt/react-modal/blob/master/lib/components/Modal.js#L43-L48