Princess Eugenie and Jack Brooksbank are postponing their son’s christening.

The couple, who had planned a ceremony for August Philip Hawke on Saturday, was told one of the guests had to self-isolate, People magazine reported on Monday.

According to multiple reports, Eugenie and her family, including Queen Elizabeth II, were supposed to gather at All Saint’s Chapel in Windsor Great Park.

Some of those expected to attend included Eugenie’s sister Princess Beatrice, who is expecting her first child this fall. She wed in the same chapel in July 2020 to her husband Edoardo Mapelli Mozzi.

In observance of coronavirus rules, no more than 30 were expected to attend the ceremony. It’s unknown whether the guest in question had COVID-19 or if they had been in contact with someone who tested positive.

Jack Brooksbank and Princess Eugenie welcomed their son in February. (Photo by David M. Benett/Dave Benett/Getty Images)

Buckingham Palace didn’t immediately respond to Fox News’ request for comment.

Just last week, Kate Middleton had to isolate herself for 10 days after it was discovered that she had come into contact with someone who tested positive.

Eugenie, 31, is the younger daughter of Prince Andrew and Sarah, Duchess of York. She is the granddaughter of the queen, 95.

The couple welcomed their son on Feb. 9 at London’s Portland Hospital. At the time, the British princess said on Instagram that the baby was named after his great-great-great-great-great grandfather Prince Albert, husband of Queen Victoria, who had Augustus as a middle name.

Princess Eugenie and Jack Brooksbank kiss after their wedding. (AP, File)

One of the baby’s middle names also pays tribute to Eugenie’s late grandfather, Prince Philip. The Duke of Edinburgh, who was hospitalized at the time of the baby’s birth, passed away on April 9 at age 99.

August is not expected to get a royal title and will be known as Master August Brooksbank. According to the outlet, he is the ninth of the queen’s 10 great-grandchildren.

Eugenie married 35-year-old Brooksbank, a businessman, in October 2018 at St. George’s Chapel at Windsor Castle.

The Associated Press contributed to this report.