Flow not typing pure fns used as React components?

example.js

// @flow
import {Component} from 'react';

export class Parent extends Component {
  render () {
    return <div>
      <JustFunction foo={2}/>
      <FullComponent foo={2}/>
    </div>
  }
}

export const JustFunction = ({foo, bar}: {foo: number, bar: number}) => <div>{foo},{bar}</div>;

export class FullComponent extends Component {
  props: {foo: number; bar: number};

  render() {
    return <div>{this.props.foo}, {this.props.bar}</div>;
  }
}

// Flow only complaints about FullComponent missing bar.
// Doesn't mention JustFunction also missing bar.