Date function in DataWindow with decimal argument

I have some datawindows with year, month, day columns that are recognised from PowerBuilder as decimal(0) (Oracle NUMBER(4)).

With PowerBuilder 10 I could add a computed field in the datawindow with the expression Date(year, month, day) without any problem.

After we migreated to PowerBuilder12.5 these computed fields are invalid now, and I have to convert these columns to int or number - i.e. Integer(string(year))