You'd think an Irish brewery would be able to get the shamrock right.
Ahead of St Patrick's Day which is celebrated on the 17 March, the Canadian branch of Guinness posted adverts around some train stations, with one fatal error:
In place of the shamrock - Ireland's national symbol - was the four-leaf clover, which has absolutely nothing to do with the country.
The three-leafed clover was said to have been used by St Patrick to demonstrate the Holy Trinity - the Father, the Son and the Holy Spirit.
Hence its very relevant use on one of Ireland's holiest of days.
Twitter reacted accordingly.
'Know the one that's too many...'
Cheers, Guinness. Job well done.
A representative for Guinness told indy100
It was a really small scale activity, and a genuine mistake. The posters have since been removed.