JDBC driver rewrites result of query with NULLs

select distinct year(regtime) from dwh.DimUser

JDBC driver > 2.5.5:

expr_0
(null)
(null)
(null)
(null)
(null)
(null)

JDBC driver 2.5.5 or ( > 2.5.5 and ?UseNativeQuery=1):

year(regtime)
2013
2011
2012
(null)
2015
2014