diff --git a/beacon-chain/blockchain/process_attestation.go b/beacon-chain/blockchain/process_attestation.go
index 372498c54..cbacc7e6d 100644
--- a/beacon-chain/blockchain/process_attestation.go
+++ b/beacon-chain/blockchain/process_attestation.go
@@ -108,7 +108,7 @@ func (s *Service) onAttestation(ctx context.Context, a *ethpb.Attestation) ([]ui
 	}
 
 	// Verify attestations can only affect the fork choice of subsequent slots.
-	if err := helpers.VerifySlotTime(genesisTime, a.Data.Slot+1); err != nil {
+	if err := helpers.VerifySlotTime(genesisTime, a.Data.Slot); err != nil {
 		return nil, err
 	}