React propType error issue

Open console and run... Only two warnings?

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.24/browser.js"></script>
<script src="https://fb.me/react-with-addons-15.0.1.js"></script>
<script src="https://fb.me/react-dom-15.0.1.js"></script>
<script src="https://facebook.github.io/react/js/jsfiddle-integration-babel.js"></script>

<div id="container1">
  <!-- This element's contents will be replaced with your component. -->
</div>


<div id="container2">
  <!-- This element's contents will be replaced with your component. -->
</div>


<div id="container3">
  <!-- This element's contents will be replaced with your component. -->
</div>

JavaScript 1.7

// Open console to see the error messages

// Hello1
class Hello1 extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    return <div > hello1 < /div>;
  }
}

// Hello1 propTypes
Hello1.propTypes = {
  prop1: React.PropTypes.string.isRequired,
}

// Hello2
class Hello2 extends React.Component {
  constructor(props) {
    super(props);
  }
  render() {
    return <div > hello2 < /div>;
  }
}

// Hello2 propTypes
Hello2.propTypes = {
  prop1: React.PropTypes.string.isRequired,
}


// Render Hello1 - propType error
ReactDOM.render( < Hello1 / > ,
  document.getElementById('container1')
);

//Render Hello2 - propType error
ReactDOM.render( < Hello2 / > ,
  document.getElementById('container2')
);


//Render Hello1 again - no propType error?
ReactDOM.render( < Hello1 / > ,
  document.getElementById('container3')
);