Double negation in CriteriaBuilderImpl

org.hibernate.jpa.criteria.CriteriaBuilderImpl cb

If double negation is used:
cb.not(cb.isNotNull(parameter))
cb.not(cb.not(cb.isNull(parameter)))

Actual sql query result:
parameter is NOT null

Expected sql query result:
parameter is null

For versions 4.2.8, 4.2.6 it works fine.