Add the keyword “class” just before UGameCharacter*. Since the header doesn’t know what UGameCharacter is (without including the UGameCharacter header file which you don’t want to do unless you absolutely have to) you need to tell it that it is a class pointer. This way the compiler can allocate enough memory for “some kind of class pointer”, and by including the UGameCharacter header in the cpp file the compiler can finally resolve what kind of pointer it is.