Last week, a framed copy of Banksy’s famous “Girl with Balloon” work self-shredded just moments after being auctioned for $1.4 million at Sotheby’s. The shredding (which some speculate Sotheby’s was in on) transformed the print into performance art, which then made it the most expensive piece of performance art ever sold at auction. But there’s more. Because the shredding was an intentional decision by the artist, it may be worth double what it sold for. It’s no longer one of many “Girl with Balloon” prints, but a one-of-a-kind Banksy performance piece.

This is all to say... don’t shred your own Banksy prints and expect to get the same results.

Unfortunately, this is a warning that has already been given but apparently ignored. On October 6th, online art auction platform MyArtBroker tweeted it had “a number of #Banksy print owners contact us today asking if they shred their artwork will it be worth more.” Two days later MyArtBroker claimed someone did just that — shredded a limited edition “Girl with Balloon” print in order to try and raise the value of the work.

MyArtBroker says the piece is one of a numbered edition of 600 unsigned “Girl with Balloon” prints. The company does not outright confirm the work’s authenticity, but does black out the bottom right corner of the photo (where the edition number would be). The seller asked MyArtBroker to list it for a minimum of £80,000, or about double what it would fetch on the market. Not only was it rejected, the broker said the shredding reduced the print’s value from £40,000 to £1.

“We have refused to list this item for a number of reasons,” said MyArtBroker. “One of them being we just can’t believe the stupidity involved and the opportunistic vandalism.”

Here’s the difference — if Banksy decides to shred his piece in a very specific setting at a very specific time in order to add additional context, then that act becomes a part of the work. If you decide to shred your own Banksy piece because you want to imitate Banksy and potentially make more money, you’re an idiot who destroyed a famous artist’s work.

“Banksy is unique to the art world. No other artist captures the hearts and minds of the public like he does,” Ian Syer, co-founder of MyArtBroker, added. “However, when Banksy does something crazy like shredding his own artwork, it will naturally have a dramatic affect on values. What this person today seems to have done is needlessly ruin a print worth around £40k and reduce its value to almost nothing. We strongly recommend nobody else takes valuable art and tries to cash in on what history will judge a simply brilliant stunt. There are limited numbers of ‘Girl with Balloon’ prints in the world, today, we lost one and it’s a crying shame.”

If you’re lucky enough to get an authentic Banksy here’s a quick test to see if you should alter it: are you Banksy? If the answer is no, then don’t. That said, I will buy this dummy’s shredded Banksy for £2, which is twice its current market valuation.