http://bugs.winehq.org/show_bug.cgi?id=5693
--- Comment #13 from Dan Kegel dank@kegel.com 2008-11-21 22:57:04 --- I suppose you could also add the test case to http://code.google.com/p/win16test/source/browse/trunk/src/listbox.c
That would let you verify that your change does not break win16.
See http://code.google.com/p/win16test/source/browse/trunk/src/README for how to build and run the wine win16 test suite.