diff --git a/pkg/cloudprovider/providers/gce/gce_loadbalancer_naming.go b/pkg/cloudprovider/providers/gce/gce_loadbalancer_naming.go
index 1e1feeff53b..63b11eb1141 100644
--- a/pkg/cloudprovider/providers/gce/gce_loadbalancer_naming.go
+++ b/pkg/cloudprovider/providers/gce/gce_loadbalancer_naming.go
@@ -31,7 +31,12 @@ import (
 
 // Instance groups remain legacy named to stay consistent with ingress
 func makeInstanceGroupName(clusterID string) string {
-	return fmt.Sprintf("k8s-ig--%s", clusterID)
+	prefix := "k8s-ig"
+	// clusterID might be empty for legacy clusters
+	if clusterID == "" {
+		return prefix
+	}
+	return fmt.Sprintf("%s--%s", prefix, clusterID)
 }
 
 func makeBackendServiceName(loadBalancerName, clusterID string, shared bool, scheme cloud.LbScheme, protocol v1.Protocol, svcAffinity v1.ServiceAffinity) string {