Can You Spot the Error in This St. Paddy's Day Ad?

Four-leaf clovers are supposed to bring good luck, but not so much for Guinness. The Irish beer company found itself apologizing to Canadians this week after the St. Patrick's Day ads it put up around the Toronto subway system's St. Patrick Station used the wrong green symbol to commemorate the holiday, Huffington Post Canada reports. Next to the Canadian maple leaf used to illustrate March 16 on the poster, Guinness put the "preferred foliage" of a four-leaf clover to symbolize March 17.

Alas, it's not the clover that represents the Irish holiday: Ireland's patron saint used a three-leafed shamrock to mark the Holy Trinity and to help spread the word of Catholicism, the Irish Times notes. An Irish man in Toronto alerted Guinness Canada to the error, per the Daily Edge, and the company said it simply got overexcited prepping for the big day and would take the posters down. (What is a shamrock, anyway? No one seems to know for sure.)