Nintendo has warned owners of the newly-released Wii U console not to switch it off midway through an epic firmware update as doing so could brick the device.

It turns out that anyone who wanted the Wii to have features taken from the PS3 has got their desire — it’s just that unfortunately that feature is an irritating and enormous update. In this case the files themselves are around 1GB and even if you are able to download them quickly, Nintendo confirms you could be looking at an hour for the installation process.

With that in mind, it’s hardly surprising that some users got tired of waiting and powered off the machine, particularly as there appears to have been no on-screen warning or selectable option to cancel the update. Unfortunately that’s proving to be a mistake as some users who’ve done so have found their consoles become completely unresponsive. That’s particularly bad news given the Wii U has only been on sale a couple of days.

For once users outside the US who are still awaiting a local release might benefit from the delay: it’s possible, but not confirmed, that Nintendo may apply the update before shipping the console in other countries.

Those who’ve bricked their machine can call Nintendo customer service on 1-800-255-3700 to arrange a repair. LA Times reporter Ben Fritz, who was among those who turned their new toy into a “big black paperweight” says Nintendo is shipping him a replacement with the update pre-installed.

There is some good news for Wii U buyers however. Rockstar Games VP Dan Houser has said that Wii U and PC versions of Grand Theft Auto V are still “up for consideration” even though the initial release is currently scheduled for PS3 and Xbox 360 only.