MUIV_Window_Width_Visible/Screen does not work as expected

As seen in Oddysey 3.0 (64-bit) when trying to enter full screen, MUIV_Window_Width_Visible(100) should set the width of window to 100%, but it does not. The same thing happens with MUIV_Window_Height_Visible and has been reported also with _Screen variant.

Note: these values are negative and they are not cast to (IPTR) so possible wrong sign extension which would be specific to 64-bit? 