React 0.14 - Card throw

Uncaught TypeError: Can't add property onTouchTap, object is not extensible card.jsx:46

in code:

```
  if (currentChild.props.actAsExpander === true) {
    currentChild.props.onTouchTap = this._onExpandable;
    currentChild.props.style = this.mergeStyles({ cursor: 'pointer' }, currentChild.props.style);
  }
```
