The royal family attended the christening of Prince Louis, the youngest son of the Duke and Duchess of Cambridge, on Monday.

While the celebration looked joyous , one of the refreshments Prince William and the former Kate Middleton served at the private reception following the christening raised a few eyebrows: a slice of their 7-year-old wedding cake.

Guests will be served slices of christening cake, which is a tier taken from The Duke and Duchess of Cambridges wedding cake, a release from Kensington Palace said.

The two also served their wedding cake at the christenings of their older children Prince George and Princess Charlotte, per a British royal tradition that dictates that couples save tiers of their cake for such occasions.

Non-royal British couples often save the top tier of their wedding cake for the same reason, according to Kylie Carlson, the director of the International Academy of Wedding & Event Planning .