Wing Lucas Dupont ran in a fifth-minute try while penalties from scrum-half Jonathan Pelissie and fly-half Blair Stewart and a drop-goal from the latter proved enough.
The victory maintains their unbeaten home record and puts them fifth in the table, just one place and two points behind Castres.
They will now have their eye on the play-offs - the top six make it through - rather than simply retaining their top-flight status.

