diff --git a/controllers/autoscaling.go b/controllers/autoscaling.go
index a9bfdb78..84ba56f1 100644
--- a/controllers/autoscaling.go
+++ b/controllers/autoscaling.go
@@ -29,10 +29,8 @@ func (r *HorizontalRunnerAutoscalerReconciler) suggestDesiredReplicas(st scaleTa
 	metrics := hra.Spec.Metrics
 	numMetrics := len(metrics)
 	if numMetrics == 0 {
-		if len(hra.Spec.ScaleUpTriggers) == 0 {
-			return r.suggestReplicasByQueuedAndInProgressWorkflowRuns(st, hra, nil)
-		}
-
+		// We don't default to anything since ARC 0.23.0
+		// See https://github.com/actions-runner-controller/actions-runner-controller/issues/728
 		return nil, nil
 	} else if numMetrics > 2 {
 		return nil, fmt.Errorf("too many autoscaling metrics configured: It must be 0 to 2, but got %d", numMetrics)
diff --git a/controllers/autoscaling_test.go b/controllers/autoscaling_test.go
index 01b8b351..4bf9f7e1 100644
--- a/controllers/autoscaling_test.go
+++ b/controllers/autoscaling_test.go
@@ -221,6 +221,11 @@ func TestDetermineDesiredReplicas_RepositoryRunner(t *testing.T) {
 				Spec: v1alpha1.HorizontalRunnerAutoscalerSpec{
 					MaxReplicas: tc.max,
 					MinReplicas: tc.min,
+					Metrics: []v1alpha1.MetricSpec{
+						{
+							Type: "TotalNumberOfQueuedAndInProgressWorkflowRuns",
+						},
+					},
 				},
 				Status: v1alpha1.HorizontalRunnerAutoscalerStatus{
 					DesiredReplicas:            tc.sReplicas,