diff --git a/checks.go b/checks.go
index 3d63ecdee..64d61a25d 100644
--- a/checks.go
+++ b/checks.go
@@ -80,7 +80,7 @@ func checkPrecommit(ctx context.Context, maddr address.Address, si SectorInfo, t
 		return &ErrBadCommD{xerrors.Errorf("on chain CommD differs from sector: %s != %s", commD, si.CommD)}
 	}
 
-	if height-si.TicketEpoch+SealRandomnessLookback > SealRandomnessLookbackLimit(si.SectorType) {
+	if height-(si.TicketEpoch+SealRandomnessLookback) > SealRandomnessLookbackLimit(si.SectorType) {
 		return &ErrExpiredTicket{xerrors.Errorf("ticket expired: seal height: %d, head: %d", si.TicketEpoch+SealRandomnessLookback, height)}
 	}