Using showAndWait in the onFinished EventHandler of an Animation doesn't work

I want to show a modal dialog after an animation ends. For some reason, calling showAndWait in the EventHandler that gets executed after the animation ends doesn't work. A new window is shown, but it seems like nothing is drawn inside it.

This example demonstrates the issue:
public void start(Stage primaryStage) {
    Rectangle rect = RectangleBuilder.create().width(200).height(200).fill(Color.RED).build();

    StackPane root = new StackPane();
    root.getChildren().add(rect);

    Timeline animation = new Timeline();
    animation.getKeyFrames().addAll(
            new KeyFrame(new Duration(1000),
                         new KeyValue(rect.widthProperty(), 100),
                         new KeyValue(rect.heightProperty(), 100)),
            new KeyFrame(new Duration(2000),
                         new KeyValue(rect.widthProperty(), 300),
                         new KeyValue(rect.heightProperty(), 300))
    );
    animation.setOnFinished(new EventHandler<ActionEvent>() {

        @Override
        public void handle(ActionEvent t) {
            Stage stage = new Stage();
            StackPane pane = new StackPane();
            pane.getChildren().add(new Label("Hello world"));
            stage.setScene(new Scene(pane, 100, 100));
            stage.showAndWait();
        }
    });
    animation.setCycleCount(1);

    Scene scene = new Scene(root, 300, 300);
    primaryStage.setScene(scene);
    primaryStage.show();

    animation.play();
}