Error adding an external Assessment to gradebook

While trying to add add a grading item via lessons the following exception can be seen:

org.sakaiproject.lessonbuildertool.service.GradebookIfc.addExternalAssessment failed add org.springframework.orm.hibernate4.HibernateQueryException: could not resolve property: gradebook.uid of: org.sakaiproject.tool.gradebook.Assignment; nested exception is org.hibernate.QueryException: could not resolve property: gradebook.uid of: org.sakaiproject.tool.gradebook.Assignment