Application loads default widgetset js file instead of compiled one

I have an Eclipse Vaadin project in which I use a custom widget and an addon. After comiling the widgetset I verified that the resulting js file is correct.

My problem is that this js file is never loaded. Instead another js file is loaded which is the default vaadin widgetset. How can I tell my application to load the custom widgetset instead of the Vaadin default one?

Found it out myself. I had to declare @Widgetset on my UI class.