React-intl和react-router：formatRelative问题

Question

我正在使用react-router（0.13）和react-intl（1.2.0）。我在路线中有这个：

var i18n = {
    locales: ['en-US']
};

var routes = (
    <Route name='home' path='/' handler={App}>
    </Route>
);

Router.run(routes, function (Handler) {
    React.render(<Handler locales={i18n.locales} />, document.body);
});

这在App中：

var ReactIntl = require('react-intl');
var IntlMixin = ReactIntl.IntlMixin;
var FormattedRelative = ReactIntl.FormattedRelative;

var App = React.createClass({
    mixins: [IntlMixin],

    render: function() {

        var postDate = Date.now() - (1000 * 60 * 60 * 24);
        var foo = this.formatRelative(postDate); //this worked before updating to 1.2.0

        return (
            {foo}
            <FormattedRelative value={postDate}/>
        );
    }
});

命令性调用（this.formatRelative）和formatRelative的组件使用都失败了：'消息必须以String或AST的形式提供。'

我做错了什么？