Problems with add-ons when changing the package name in Eclipse

When I create a new Vaadin 7 project with Eclipse and change the package name from com.example to something else, and ad a visual add-on (like FormCheckBox or Switch ) the result is a normal checkbox.
I did the following steps for adding an Add-on:
- download the jar and put it in the WEB-INF directory
- added the dependency of the Add-on to my ivy.xml file
- checked the presence of the<ibiblio ...> part in the ivysettings.xml
- Compiled the Vaadin widgets

After deploying to a tomcat server, I get a normal checkbox.

Are there steps that I'm missing here?

Thanks for helping me out!