Spring Roo + Vaadin + @Embeddable entity

I am currently evaluating Vaadin+Roo using a simple example project with JPA (Eclipselink).
The project consists of two entities, User and UserPreferences. I have declared UserPreferences as @Embeddable using roo’s command

embeddable --class com.example.domain.UserPreferences
field string --fieldName lang --notNull true --class com.example.domain.UserPreferences

end User has a embedded field declared using

field embedded --fieldName preferences --type com.example.domain.UserPreference --class com.example.domain.User

After issuing

vaadin generate all --package ~.admin.ui --visuallyComposable true 

the result in DB and in .java files are as expected but if check the resulting web interface cannot see “lang” field in User edit form. As “lang” field is declared NotNull I get an exception from Eclipslink complaining about empty field.

What is the correct wau to use @Embeddable/@Embedded? Am I missing something?

Thanks in advance.