Strictly Come Dancing judge Motsi Mabuse will miss Saturday's show after coming to close contact with a person who tested positive for Covid-19.
In an Instagram post, Mabuse explained she was fully vaccinated, which would normally mean exemption from isolation.
However, Mabuse is currently in Germany and not able to travel back due to UK Government guidelines, which do not recognise the vaccines she received.
Singer and actress Cynthia Erivo will take her place on the panel.
It will be Erivo's second week as a judge, after last weekend.
Horwood had tested positive for Covid-19 but will return to the panel this weekend, a Strictly spokesman confirmed.
"Motsi Mabuse will not be taking part in Strictly Come Dancing this weekend," a representative for the show said on Friday.
"We are delighted that Cynthia Erivo will be joining us as a guest judge again, joining Craig Revel Horwood, Anton Du Beke and head judge Shirley Ballas on the judging panel. We look forward to having Motsi back with us next weekend."
Other stars to have missed episodes of Strictly due to Covid this year include celebrity contestants and .
Writing on Instagram, Mabuse said she was "gutted" to have to miss Strictly.
"I was contacted by NHS Test and Trace as being in close contact with someone on Sunday 21 Nov who has since tested positive," she explained.
"Being double vaccinated and booster as I am, would normally mean exemption from isolation under the close contact rules, but unfortunately German EU vaccines are not recognised and neither is my booster in this instance, so I must follow UK Government guidance and can only return after 30 November to UK."
The government website states that the EU Digital Covid Certificate (EUDCC) is not recognised as proof of vaccination for passengers travelling to the UK from Germany.
While the UK recognises the certificate for passengers travelling from some European countries, for those travelling from Germany the guidelines state: "You cannot currently use your EU DCC to verify your vaccination status via the UK passenger locator form."
It adds that people whose EUDCC was issued in Germany can use it to prove vaccination status within the UK, however it does not apply for travel.
Mabuse said: "Our health is the most important thing and luckily I have been tested multiple times this week and am negative. I am healthy, I am with my family, that's what matters! I wish everyone good luck, sending you my love. Keep dancing. Until then, lots of love and stay safe."
Also this week, the USAGovNews confirmed that Anne-Marie, Moira Stuart, Mel Giedroyc, Fred Sirieix, and Jay Blades will take part in this year's Christmas special. The sixth and final celebrity will be announced later on Friday.