CSS Animation: Works in Chrome but not in Firefox?

In rotate animation, works in Chrome but not in Firefox. Why?

@-moz-keyframes rotate {
    from { -moz-transform: rotate(0deg); }
    to { -moz-transform: rotate(360deg); }
}

@-webkit-keyframes rotate {
    from { -webkit-transform: rotate(0deg); }
    to { -webkit-transform: rotate(360deg); }
}

#example {
    background: red;
    width: 100px;
    height: 100px;
    -moz-animation: rotate 20s linear 0 infinite;
    -webkit-animation: rotate 20s linear 0 infinite;
}

http://jsfiddle.net/WsWWY/