React-router error: super expression must either be null or a function

I am new to react-router (https://github.com/rackt/react-router). I included it after react like this: <script src="http://fb.me/react-0.12.2.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/reactrouter/0.13.2/ReactRouter.js"></script> I got an error: Uncaught TypeError: Super expression must either be null or a function, not undefined What did I do wrong?