diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h
index 35d28d9f8a9b..32ca2bfee1db 100644
--- a/drivers/md/dm-verity-fec.h
+++ b/drivers/md/dm-verity-fec.h
@@ -47,7 +47,8 @@ struct dm_verity_fec {
 /* per-bio data */
 struct dm_verity_fec_io {
 	struct rs_control *rs;	/* Reed-Solomon state */
-	int erasures[DM_VERITY_FEC_MAX_RSN];	/* erasures for decode_rs8 */
+	/* erasures for decode_rs8 */
+	int erasures[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN + 1];
 	u8 *output;		/* buffer for corrected output */
 	unsigned int level;		/* recursion level */
 	unsigned int nbufs;		/* number of buffers allocated */