ReactCSSTransitionGroup componentWillLeave not called

Im trying to play around with ReactCssTransition but somehow the event is not called(componentWillLeave)

Here's my component

import React, { Component } from 'react'
import TransitionGroup from 'react-addons-css-transition-group'

export default class TransitionComponent extends Component {

  constructor(props) {
    super(props);
  }

  render() {
    return (
      let {componentKey} = this.props
      <TransitionGroup transitionName="example" transitionEnterTimeout={500} transitionLeaveTimeout={500}>
        <Item key={"item"+componentKey} />
      </TransitionGroup>
    );
  }
}

And the child component

class Item extends Component {

  componentDidEnter() {
    console.log("component did enter");
  }

  componentWillLeave(callback) {
    console.log("component will leave");
  }

  render() {
    return (
      <div>Item</div>
    )
  }
}

Any clue? Thanks!