Strange behavior in html builder

Hi All!
Came across with such a problem. I have application with main window which contain header(horizontal layout) and main view(horizontal spit panel)

@Named("MainView")
public class MainView extends HorizontalSplitPanel {

All work fine, before I insert additional annotation

@Named("MainView")
@SessionScoped
public class MainView extends HorizontalSplitPanel {

vaadin reduced mainview component size to 1px!!!
I attached 2 files before.png & after.png that show how one annotation affects html code generation.

Does anyone encountered this problem?

Thanks!

P.S.
I use vaadin 6.8.12
13308.png
13309.png