diff --git a/controllers/cluster_controller.go b/controllers/cluster_controller.go
index 385dbe2df0bd..cf5e93b5a049 100644
--- a/controllers/cluster_controller.go
+++ b/controllers/cluster_controller.go
@@ -326,7 +326,8 @@ func (c *clusterDescendants) length() int {
 	return len(c.machineDeployments.Items) +
 		len(c.machineSets.Items) +
 		len(c.controlPlaneMachines.Items) +
-		len(c.workerMachines.Items)
+		len(c.workerMachines.Items) +
+		len(c.machinePools.Items)
 }
 
 func (c *clusterDescendants) descendantNames() string {
diff --git a/controllers/cluster_controller_test.go b/controllers/cluster_controller_test.go
index 4636d03e5a3b..d6facad2062e 100644
--- a/controllers/cluster_controller_test.go
+++ b/controllers/cluster_controller_test.go
@@ -667,6 +667,50 @@ func TestFilterOwnedDescendants(t *testing.T) {
 	g.Expect(actual).To(Equal(expected))
 }
 
+func TestDescendantsLength(t *testing.T) {
+	g := NewWithT(t)
+
+	d := clusterDescendants{
+		machineDeployments: clusterv1.MachineDeploymentList{
+			Items: []clusterv1.MachineDeployment{
+				newMachineDeploymentBuilder().named("md1").build(),
+			},
+		},
+		machineSets: clusterv1.MachineSetList{
+			Items: []clusterv1.MachineSet{
+				newMachineSetBuilder().named("ms1").build(),
+				newMachineSetBuilder().named("ms2").build(),
+			},
+		},
+		controlPlaneMachines: clusterv1.MachineList{
+			Items: []clusterv1.Machine{
+				newMachineBuilder().named("m1").build(),
+				newMachineBuilder().named("m2").build(),
+				newMachineBuilder().named("m3").build(),
+			},
+		},
+		workerMachines: clusterv1.MachineList{
+			Items: []clusterv1.Machine{
+				newMachineBuilder().named("m3").build(),
+				newMachineBuilder().named("m4").build(),
+				newMachineBuilder().named("m5").build(),
+				newMachineBuilder().named("m6").build(),
+			},
+		},
+		machinePools: expv1.MachinePoolList{
+			Items: []expv1.MachinePool{
+				newMachinePoolBuilder().named("mp1").build(),
+				newMachinePoolBuilder().named("mp2").build(),
+				newMachinePoolBuilder().named("mp3").build(),
+				newMachinePoolBuilder().named("mp4").build(),
+				newMachinePoolBuilder().named("mp5").build(),
+			},
+		},
+	}
+
+	g.Expect(d.length()).To(Equal(15))
+}
+
 func TestReconcileControlPlaneInitializedControlPlaneRef(t *testing.T) {
 	g := NewWithT(t)