USB Printer Stopping Sleep State

Hi,

I've a USB printer that is stopping my PC from staying in the sleep state,
powercfg seems to think it is my mouse/keyboard that are at fault but
disabling their ability to wkae the system doesn't prevent the problem. By
sytematically removing each USB device I isolated the printer as the problem
(a Brother DCP7010) and the system remains asleep without it attached.
There's nothing obvious in the settings nor in Device Manager to change this
and I've updated the drivers with no luck. Am I missing something obvious or
is there another solution?

Thanks