Default [Q] Device not detected in fastboot mode

# fastboot devices
# adb devices
List of devices attached 

# lsusb | grep Motorola
Bus 001 Device 010: ID 22b8:2e80 Motorola PCS 
My moto g is not detected in fastboot mode. I can't flash stock roms.
I have tried on three different operating systems: ubuntu, archlinux and windows 7.
Any idea?