People traditionally dress up in green to celebrate St Patrick's Day on March 17, donning leprechaun costumes and painting their faces with the colors of the Irish flag or the shamrock, the three-leafed plant that is the symbol of Ireland.

And those who are fans of President Donald Trump can also buy a green cap to top off their outfits, featuring "Make America Great Again" on the front, and a plant motif on the back. But there's one problem: the motif sewn into the hat is actually a four-leaf clover, not a shamrock.

TWEET

People posting on Twitter noticed that the "Official Make America Great Again Green Hat" featured the wrong symbol used hashtags including #fakefacts and #fakerock.

Trump's merchandise website encourages fans to "Capture the luck of the Irish" by buying the hat. However those who want to will be disappointed: the $50 cap – the most expensive listed on the site - has sold out.

CNBC.com has contacted the Trump Make America Great Again Committee, which runs the online shop, but has not received a response.

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