[U-Boot] fw_setenv writes to bootdelay but not ethaddr

root:/> fw_setenv bootdelay 3

MTD_open

MTD_ioctl

MTD_ioctl

MTD_read

MTD_close

MTD_open

MTD_ioctl

MTD_ioctl

MTD_ioctl

nand_erase_nand: start = 0x000000060000, len = 131072

MTD_write

MTD_ioctl

MTD_close

nand_sync: called

root:/>

root:/> fw_setenv ethaddr X1:X2:X3:X4:X5:X6

MTD_open

MTD_ioctl

MTD_ioctl

MTD_read

MTD_close

Can't overwrite "ethaddr"

root:/>

Where Xn is a valid MAC address.