And also with the optiboot makefile:
atmega328_isp: atmega328
atmega328_isp: TARGET = atmega328
atmega328_isp: MCU_TARGET = atmega328p
# 512 byte boot, SPIEN
atmega328_isp: HFUSE = DE
# Low power xtal (16MHz) 16KCK/14CK+65ms
atmega328_isp: LFUSE = FF
# 2.7V brownout
atmega328_isp: EFUSE = FD
atmega328_isp: isp
(EFUSE == 0xFD is the same as 5, depending on whether the "unused" bits are set to 1 or 0.)