Office programs do not show up in "default programs"

My MS Office programs do not show up in "Default Programs" listing in Control Panel. The programs are all properly associated with their own file type, and show up in "Open with" when write clicking the file. But, in the listing of "Default Programs" under the "Set Default Programs" tab they are not listed. How do I get them to show up there? (I need the programs to be listed there so that another program which checks that list will work properly".)