diff --git a/controllers/hpa.go b/controllers/hpa.go
index 40c9a50741a..13b1d545e6f 100644
--- a/controllers/hpa.go
+++ b/controllers/hpa.go
@@ -111,7 +111,8 @@ func (r *ScaledObjectReconciler) updateHPAIfNeeded(logger logr.Logger, scaledObj
 		return err
 	}
 
-	if !equality.Semantic.DeepDerivative(hpa.Spec, foundHpa.Spec) {
+	// DeepDerivative ignores extra entries in arrays which makes removing the last trigger not update things, so trigger and update any time the metrics count is different.
+	if len(hpa.Spec.Metrics) != len(foundHpa.Spec.Metrics) || !equality.Semantic.DeepDerivative(hpa.Spec, foundHpa.Spec) {
 		logger.V(1).Info("Found difference in the HPA spec accordint to ScaledObject", "currentHPA", foundHpa.Spec, "newHPA", hpa.Spec)
 		if r.Client.Update(context.TODO(), hpa) != nil {
 			foundHpa.Spec = hpa.Spec