Credit: Camera Press/Retna Ltd.

Pippa Middleton is waxing up her skis for a good cause!

On Sunday, Middleton, 28, will hit the slopes with her brother James, 24, for the Vasaloppet, a 56-mile cross-country ski marathon in the Swedish mountains.

The reason? Race spokesman Per Strid says the siblings of Kate, the Duchess of Cambridge, are raising funds for Magic Breakfast, a charity that delivers free, healthy breakfasts to children at U.K. primary schools.

Last year 16,000 people took part in the competition, which is touted as one of the world's oldest cross-country races.