“You sit on a throne of lies,” said Buddy the Elf. Buddy, played by comedian Will Ferrel in the hit 2003 Christmas comedy Elf, was telling a mall a Santa Clause that he wasn’t really Santa Clause. And if you own a bottle of vintage whisky, you might be saying the same thing to your seller. A new study has been published that says a third of all vintage whisky is a fake.

The study was conducted in Scotland at the East Kilbride-based Scottish Universities Environmental Research Centre (SUERC).

First reported on by the British Broadcast Company (BBC) the SUERC found that 21 out of 55 bottles of whisky were either complete fakes, or not distilled in the year published on the bottle. By studying isotopes in the whisky, and using a complicated scientific process, SUERC was able to determine the fakes.

The whiskys were sent for analysis by Rare Whisky 101 (RW101). RW101 is a whisky broker and tries to keep tabs on all the fake whisky in the world. The reason for this study is what they call the, “Continued Proliferation of Fake Scotch Whisky.” They say whisky values are skyrocketing. And because of that, the production of fake whisky is rapidly increasing.

“It is impossible to place an estimate on the value of fake bottles/liquid in the broader market. However, what we can say with 100% certainty is we are observing an increasing number of fakes across all value segments.”

If you’re buying fancy whisky this holiday season, make sure you are getting the real thing, and not a knock off. A few easy ways to avoid knockoff whisky are to not buy them online at peer-to-peer auctions, don’t buy them at in-person auctions, and if it’s too good to be true then it probably is.