Ulster have finished the pool stage of the Heineken Cup with a narrow win over Castres in a low-scoring match.
Castres were the stronger side in the first half. Remi Lamerat scored an early try, supplemented with a Rory Kockott penalty to give the hosts a 8-6 lead at half time.
A defensively-strong second half for both sides saw few try opportunities for either side.
Ruan Pienaar added the only points of the second 40 minutes with a penalty in the 63rd minute, his third successful kick of the match.
Pienaar had a chance to extend Ulster's lead five minutes from full time, but his effort failed to find the uprights.
The win ensures that Ulster will finish top of pool four with five wins from six games.
