The Apple Watch is smart enough to protect your data. It knows when it’s been taken off your wrist, and it won’t let itself be unlocked without a passcode.
But it’s not smart enough to destroy its resale value should it leave your wrist for good.
The hole in the device’s security measures was documented Wednesday by iDownloadBlog’s Jeff Benjamin, who helpfully provided the how-to video attached below. It shows how, without a passcode, you can reset the watch to factory condition, ready to paired with someone else’s iPhone.
The iPhone used to be just as easy to reset, making it a popular target for thieves. Then, two years ago, with the release of iOS 7, Apple added a “kill switch,” a lock that prevents the phone from being activated without the owner’s name and password. The news quickly spread, and within 12 months, iPhone thefts had fallen 40% in San Francisco, 25% in New York City and 50% in London.
News of the Watch’s vulnerability is already out. Apple can’t make a Find My Watch app because the device doesn’t have its own cellular radio. But Apple could make a kill switch that would prevent resets without proper credentials.
Until it does, be careful where you flash that Apple bling.
Follow Philip Elmer-DeWitt on Twitter at @philiped. Read his Apple (AAPL) coverage at fortune.com/ped or subscribe via his RSS feed.