diff --git a/drivers/infiniband/hw/mthca/mthca_mr.c b/drivers/infiniband/hw/mthca/mthca_mr.c
index fdb576dcfaa852bd859d8c4ed8d72f9141148c5f..ee561c569d5f0c95c17fc2fe659274d9069696ba 100644
--- a/drivers/infiniband/hw/mthca/mthca_mr.c
+++ b/drivers/infiniband/hw/mthca/mthca_mr.c
@@ -835,6 +835,7 @@ void mthca_arbel_fmr_unmap(struct mthca_dev *dev, struct mthca_fmr *fmr)
 
 	key = arbel_key_to_hw_index(fmr->ibmr.lkey);
 	key &= dev->limits.num_mpts - 1;
+	key = adjust_key(dev, key);
 	fmr->ibmr.lkey = fmr->ibmr.rkey = arbel_hw_index_to_key(key);
 
 	fmr->maps = 0;