Forget Dry January, it could be Dry December for Guinness fans after pub landlords were caught out by soaring demand for the stout due to a newfound popularity with Gen Z who like to pose on social media, pint in hand.

With its thick white foamy head and agonising 119.5 second pour time, the black stuff was traditionally favoured by older men and rugby teams. But all bets are off on who is going to order a pint thanks to a celebrity-fuelled renaissance which has Kim Kardashian and Olivia Rodrigo among the unlikely poster children.

But Guinness’s growing fashionability is causing a headache for publicans this Christmas party season, with the drink’s owner, Diageo, forced to ration weekly orders after a period of extraordinary demand. The company cannot increase supply as its Dublin brewery is already working at full capacity, it is understood.

A spokesperson for Diageo said that, over the past month, it had “seen exceptional consumer demand for Guinness in Great Britain”. “We have maximised supply and we are working proactively with our customers to manage the distribution to trade as efficiently as possible,” they added.

Diageo has been upping its marketing efforts and working with influencers over the past few years to raise Guinness’s profile, and it has worked. Kardashian made headlines last year when she supped on a pint in a London pub, meanwhile Rodrigo wore a “Guinness is good 4U” T-shirt when performing in Dublin this year.

While Guinness has been winning over women and young people in general, the recent rugby internationals will also have contributed to the pressure on supplies. Nevertheless the brand is defying gravity in a moribund market. While the overall amount of beer sold fell slightly between July and October, during the same period demand for draft Guinness was up by more than 20%, according to industry analysts CGA.

The brand has benefited from viral marketing that features drinkers sharing pictures and videos of the perfect or not-so-perfect pint (the Shit London Guinness Instagram account has a huge following). This amateur content often involves the “tilt test” whereby drinkers tilt their glass at a 45-degree angle. If it is up to creamy standard, the contents will not spill out, it is claimed.

This renewed appreciation for the 265-year-old drink has seen The Devonshire pub, a revived institution in London’s Soho, draw huge crowds based on its claim to pour the best pint of Guinness in the capital. The well-known publican Oisin Rogers brought in barmen from Dublin’s Kehoes pub, itself an institution for a pint of Guinness, to add authenticity.

But it is not time to start stockpiling in the supermarket yet. Wetherspoon’s, one of the country’s biggest landlords with more than 800 pubs, has reassured that it had a “full supply of Guinness”.

“The gods of fashion have smiled upon Guinness, previously consumed by blokes my age, but now widely adopted by younger generations,” said Tim Martin, Weatherspoon’s 69-year-old founder. The company hoped Guinness would be able to “ramp up production … which it has always managed to do in previous Christmas periods”.

The rationing of liquid (black) gold is only happening in Great Britain and should not last, as Diageo has been pumping money into its St James’s Gate brewery in Dublin and is also building a new €200m (£166m) brewery in County Kildare.