JPA calling stored procedure with argument

I have this procedure in my postgreSQL database:

CREATE OR REPLACE FUNCTION getItemsForCategory(categoryId integer)
  RETURNS SETOF ITEM AS $_$
DECLARE
  result ITEM;
BEGIN
  FOR result IN SELECT *
                FROM item it
                  JOIN item_category itcat ON it.id = itcat.item_id WHERE itcat.category_id = categoryId LOOP
    RETURN NEXT result;
  END LOOP;

END; $_$ LANGUAGE 'plpgsql';

which works excellent using terminal, but I have trouble with calling it using JPA. Here is my code snippet(4 is value of argument cateforyId):

 transactions.begin();
 final StoredProcedureQuery storedProcedureQuery = entityManager.createStoredProcedureQuery("getItemsForCategory");
 storedProcedureQuery.setParameter(1,4).execute();
 final List itemEntityList = (List) storedProcedureQuery.getResultList();
 transactions.commit();

after ruing code above I receive this error:

Exception in thread "main" java.lang.IllegalArgumentException: 
You have attempted to set a parameter at position 1 which does not exist in this query string getItemsForCategory

Has anyone some idea how to set the value of argument correctly? I've also tried to set parameter using 0 instead of 1, calling setParameter with others datatypes of arguments (String,Object) but everytime I am receiving familiar kind of error like the one, which is shown there. Thank you very much