CSSTransition group not working (undefined) React.js

I am calling the CSS Transition Group property from React.

In my js file:

var ReactCSSTransitionGroup = React.addons.CSSTransitionGroup;

      

        
        
        
      

    

I am getting this exact error:

Uncaught TypeError: Cannot read property 'CSSTransitionGroup' of undefined

      

        
        
        
      

    

Any idea?