diff --git a/consensus/istanbul/backend/engine.go b/consensus/istanbul/backend/engine.go
index a0482b3d7c..4895193344 100644
--- a/consensus/istanbul/backend/engine.go
+++ b/consensus/istanbul/backend/engine.go
@@ -429,7 +429,7 @@ func (sb *Backend) EpochSize() uint64 {
 
 // LookbackWindow returns the size of the lookback window for calculating uptime (in blocks)
 func (sb *Backend) LookbackWindow(header *types.Header, state *state.StateDB) (uint64, error) {
-	if !sb.chain.Config().IsCelo1(header.Number) {
+	if !sb.chain.Config().IsDonut(header.Number) {
 		return sb.config.LookbackWindow, nil
 	}
 	return blockchain_parameters.GetLookbackWindow(header, state)