Javafx ImageView Tooltip style - css

Question

I have made a global style to be applied to all tooltips, and it is working correctly except when then the tooltip is installed onto an ImageView. If I add the tooltip to the ImageView's parent (a HBox), the styling is correct, so it can't be a problem with the stylesheet not being added.
The css style looks like this:
.tooltip
{
-fx-border-color: gray;
-fx-border-radius: 5.0 5.0 5.0 5.0;
-fx-background-radius: 5.0 5.0 5.0 5.0;
-fx-background-color: white;
-fx-text-fill: black;
-fx-wrap-text: true;
}
Adding tooltip to imageview (style doesn't work):
Tooltip.install(imageviewFormat, formatTooltip);
Adding tooltip to parent (style does work):
Tooltip.install(imageviewFormat.getParent(), formatTooltip);
Am I doing something stupid here, or does ImageView not inherit the css from its parent. Any insight would be appreciated.
Update
The following example has this behavior, where style.css contains the same tooltip styleclass.
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Tooltip;
import javafx.scene.image.ImageView;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
public class Test extends Application
{
public static void main(String[] args) throws Exception
{
launch(args);
}
#Override
public void start(Stage primarystage) throws Exception
{
HBox root = new HBox();
root.getStylesheets().add(getClass().getResource("style.css").toExternalForm());
ImageView imageView = new ImageView("http://www.samjarman.co.nz/images/so.png");
root.getChildren().add(imageView);
Tooltip.install(imageView, new Tooltip("Tooltip")); // Doesn't work
// Tooltip.install(imageView.getParent(), new Tooltip("Tooltip")); // Works
Scene scene = new Scene(root);
primarystage.setScene(scene);
primarystage.show();
}
}
Thanks