Qt Creator is not generating UI header files in the build folder.

Hi Everyone,
I am using the Qt creator to modify a GUI for my c++ project which was initially written in qt 4.6.0. Now I am using Qt Commercial 4.8.3 and when I have used the design options in Qt creator it has generated ui_filename.h in my build folder and working fine. But my colleagues (who are using other version of Qt) have some missing ui_filename.h files when they built the same project. After investigation I found that they only don't have those (ui_filename.h) files in the build folder which is associated with the .ui modified by me.

Any thought on this will be very helpful.

Thanks.
Pritimoy