Police are warning holiday shoppers scammers have been placing fake barcodes on gift cards at stores.

“Scammers are printing out their own barcodes and placing them over the actual gift card barcode at local retailers,” the Boca Raton Police Department wrote on Facebook. “When the card is activated, the money is added to the scammer’s card instead of the card being purchased.”

The department said fraudulent barcodes were recently discovered by a Walgreens store employee.

Police recommend making sure the barcode on the back of the card matches the number on the packaging itself and they suggested checking for stickers placed over the barcode and choosing a gift card in the middle or back of the rack.

“Criminals will likely go for the front cards because they can commit the crime more quickly,” the department said.