diff --git a/pkg/agent/controller/managedclusterrolebinding_controller.go b/pkg/agent/controller/managedclusterrolebinding_controller.go
index dcd2e899..f119048f 100644
--- a/pkg/agent/controller/managedclusterrolebinding_controller.go
+++ b/pkg/agent/controller/managedclusterrolebinding_controller.go
@@ -205,7 +205,7 @@ func (r *ManagedClusterRoleBindingReconciler) SetupWithManager(mgr ctrl.Manager)
 }
 
 func getSubject(managedCRB authzv1alpah1.ManagedClusterRoleBinding) []rbac.Subject {
-	var subs []rbac.Subject
+	subs := make([]rbac.Subject, 0, len(managedCRB.Subjects))
 	for _, sub := range managedCRB.Subjects {
 		subs = append(subs, rbac.Subject{
 			APIGroup: sub.APIGroup,