ATXmega writing fuses avrdude

Hi guys.

i have been programming the atxmega with avrdude. i can chip erase, loag hex files get verbosa information but I cannot write to fuse 0-5. i can write to the lock bit. Does anyone have any ideas?

code:

avrdude -c stk500v2 -p x128a1 -P usb -u -U fuse0:w:0xff:m