Uncaught TypeError: Cannot read property 'shape' of undefined

I am getting an Error in declaring the shape of the array, and I cant find out why. Please help, thank you.

Application.propTypes = { title : React.PropTypes.string, players : React.PropTypes.arrayOf(React.Proptypes.shape({ name : React.PropTypes.string.isRequired, score : React.PropTypes.number.isRequired, })).isRequired, }