Problem with Specification query on App Engine/Datanucleus

I'm encountering a problem using Spring Data JPA 1.2.0 in combination with Datanucleus 3.1.3 on App Engine.

Code:

---

public interface CustomerRepository extends JpaRepository<Club, Long>, JpaSpecificationExecutor<Club> {

    List<Customer> findByLastImportDateGreaterThan(Date lastImportDate, Pageable pageable);
}

---

This works perfectly and the query being executed is:
"SELECT FROM com.mycomp.domain.Customer DN_THIS WHERE (DN_THIS.lastImportDate > :DN_PARAM_0)"

Now when I try to the same using a Specification like:

Code:

---

    public static Specification<Customer> eligibleForImport(Date date) {
        return new Specification<Customer>() {
            @Override
            public Predicate toPredicate(Root<Customer> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                return cb.greaterThan(root.<Date> get("lastImportDate"), date);
            }
        };
    }

---

The compiled query looks like:
"SELECT FROM com.mycomp.domain.Customer DN_THIS WHERE (DN_THIS.lastImportDate > Sat Aug 04 06:04:38 CEST 2012)"

>> Note the actual date being printed..

And this gives a exception like:

[INFO] org.springframework.orm.jpa.JpaSystemException: expected ')' at character 31 in "(DN_THIS.lastImportDate > Sat Aug 04 06:04:38 CEST 2012)"


I wonder if this is a problem on Datanucleus/App Engine side or not.
I've enabled debug logging for Spring Data but don't see anything being logged btw.
log4j.category.org.springframework.data.jpa = DEBUG


Any suggestions?