Stepper and FieldGroup.buildAndBind.

I have two String properties that are integer numbers in fact and I want to put their values to IntStepper.
I generate my Form using FieldGroup.buildAndBind() method. And when I pass IntStepper as a field type, I receive the following error:

Should I somehow call parseStringValue or is it better to convert String to Integer in Bean getter/setter ?


updated

If I try to bind value in Stepper straight with property, I receive the following message instead of Stepper:

I followed the instructions, but update of widgetset didn’t help me. But still I need to build and bind it via FieldGroup.

I use Vaadin 7 beta11 and Stepper 2.0.1.