EditorType in ds.xml com Custom DateItem

SmartGWT Framework: v9.0p_2014-02-26/PowerEdition Deployment 2014-02-26
Browse: FireFox 24.3.0

I created a subclass of DateItem
public class DateItemExt extends DateItem {
}


In ds.xml added the EditorType
<field name="PRG_DataInicio" title="Data Início" type="date" editorType="DateItemExt"/>

When I connect to the datasource DynamicForm results the following error

Exception caught: (TypeError) @ com.smartgwt.client.widgets.form.DynamicForm :: create () ([]): _5 is undefined
See the Development console log for details.

NOTE: I am trying to use reflection according link unsuccessfully
http://www.smartclient.com/smartgwt/...eflection.html