I believe this problem has been fixed in the new 2015.0825 release of DBD::Informix. There's a minor issue in DBD::Informix::TechSupport that means there will be another release very shortly (maybe 2015-08-26).
--
Jonathan Leffler <jonathan.leffler@gmail.com>
Guardian of DBD::Informix 2015.0825 -- see
http://dbi.perl.org/
"I don't suffer from insanity - I enjoy every minute of it!"