Person with speaking role missing from movie cast list

I was recently browsing IMDb, looking at the page for the Robert Altman movie 'Brewster McCloud' (one of my favorite movies). I remember watching it many years ago and there was a black actor playing Weeks' chauffeur in it. I believe his character's name was Norwood. It was a small role but the actor did have at least one spoken line. Why isn't he listed in the cast list? He should be. Please fix this.