Guinness, the Irish stout that once famously advertised itself under the slogan “Guinness is good for you,” took a step this week to inject 21st-century food culture into its 256-year-old product. Guinness is going vegan.

The company announced on Monday that starting at the end of 2016, its beer will no longer contain trace amounts of fish bladder, an integral part of its filtration process.

Few customers — except perhaps vegans and vegetarians who enjoy a pint — were probably even aware that the famous inky-black drink contained any fish parts at all. But it is actually quite common for cask beers to be filtered using isinglass, a gelatinlike substance derived from the dried swim bladders of fish that is used to separate out unwanted solids like yeast particles from a brew, the company said.

“Isinglass has been used widely within the brewing industry as a means of filtration for decades,” the company said in a statement on Monday after a report in The Times of London. “However, because of its use we could not label Guinness as suitable for vegetarians and have been looking for an alternative solution for some time.”