This is a bug in F20 installer that still believes it is in UEFI native mode even if the
noefi parameter is passed.
There is an updates image for the installer which fixes this issue available at https://www.happyassassin.net/updates/updates-1047904.img. Instructions on using an updates image are available here: in short, simply pass the parameter
inst.updates=https://www.happyassassin.net/updates/updates-1047904.imgto the installer.