react-helmet with react_on_rails server side rendering

helmet.js

import React, { Component, PropTypes } from 'react'
import ReactHelmet from 'react-helmet'

class PlainComponent extends Component {
  render () {
    return null
  }
}

export default class Helmet extends Component {
  static propTypes = {
    helmet: PropTypes.object
  }

  render () {
    const { helmet } = this.props

    if (typeof document === 'undefined') {
      return <PlainComponent />
    } else {
      return <ReactHelmet {...helmet} />
    }
  }
}