Bristol's British and Irish Cup game at Aberavon will be replayed after the initial fixture was abandoned because of a deep hole in the pitch.
The referee called off the game on 19 October after 69 minutes for safety reasons, with Bristol leading 24-20.
A Rugby Football Union organising committee met this week and decided against letting the result stand.
The replay must be at the same venue on a date suitable to both clubs before the conclusion of the pool stages.
Both clubs have the right to appeal the decision, but if no appeal is made, they have four weeks to agree a new date.