Is extended_fuses setting wrong?

[gitgrimbo]

boards.txt#L11 has the following extended_fuses setting:

atmega328bb.bootloader.extended_fuses=0x05

But when I use this to burn a bootloader on an ATmega328P my chip does not start up on 3.3V, but works at 4.23V, 4.8V and 5V.

Changing to the following works:

atmega328bb.bootloader.extended_fuses=0x02

So I think those 3 bits are inverted, i.e. 0000 0101 (0x05) should be 0000 0010 (0x02) for 2.7V brownout detection.

edit - I've just realised that running at 3.3V may not even be one of your goals. Maybe add a second board setting for 3.3V?