Performing a "Modifying query" generates an error

The execution of a "Modifying query", defined as follows:

public interface EventoCalendarioRepository extends JpaRepository<EventoCalendario, Integer> {
@Transactional
@Modifying
@Query("update EventoCalendario ec set ec.dataEstinzione = null, ec.ottemperato = false where ec.id = :id")
Integer resetStatoEvento(@Param("id") Integer id);
}

invoking the url with the GET method:
http://localhost:8080/laweb4/eventoCalendario/search/resetStatoEvento?id=55074

generates a response with error:
Request URL:http://client-wi7-rzu2:8080/laweb4/eventoCalendario/search/resetStatoEvento?id=55074
Request Method:GET
Status Code:400 Bad Request
Request Headersview source
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8
Accept-Encoding:gzip,deflate,sdch
Accept-Language:it-IT,it;q=0.8,en-US;q=0.6,en;q=0.4
Connection:keep-alive
Cookie:JSESSIONID=9436BEBA86AC23EA6286FB5F7C23A50F
Host:client-wi7-rzu2:8080
User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.37 Safari/537.36
Query String Parametersview sourceview URL encoded
id:55074
Response Headersview source
Connection:close
Content-Encoding:gzip
Content-Type:application/json
Date:Thu, 06 Jun 2013 12:17:20 GMT
Server:Apache-Coyote/1.1
Transfer-Encoding:chunked
Vary:Accept-Encoding

with this response:
{"cause":null,"message":"java.lang.ClassCastException@453fd696"}

N.B.
The command to update the db is successful

To me it seems a bug, what do you think?

Start with the EventoCalendarioRepository.resetStatoEvento method and the /eventoCalendario/search/resetStatoEvento route described in the report. Reproduce the GET request with id=55074, then trace how the successful modifying-query result is converted into the HTTP response; done means the update still succeeds without the reported ClassCastException and the endpoint returns a valid response.