diff --git a/controllers/apps/v2beta1/sync_sets.go b/controllers/apps/v2beta1/sync_sets.go
index c2808e63a..8da41f39a 100644
--- a/controllers/apps/v2beta1/sync_sets.go
+++ b/controllers/apps/v2beta1/sync_sets.go
@@ -41,7 +41,7 @@ func (s *syncSets) reconcile(ctx context.Context, instance *appsv2beta1.EMQX, r
 	_, _, oldStsList := getStateFulSetList(ctx, s.Client, instance)
 	stsDiff := int32(len(oldStsList)) - *instance.Spec.RevisionHistoryLimit
 	if stsDiff > 0 {
-		for i := 0; i < int(rsDiff); i++ {
+		for i := 0; i < int(stsDiff); i++ {
 			sts := oldStsList[i].DeepCopy()
 			// Avoid delete stateful set with non-zero replica counts
 			if sts.Status.Replicas != 0 || *(sts.Spec.Replicas) != 0 || sts.Generation > sts.Status.ObservedGeneration || sts.DeletionTimestamp != nil {
diff --git a/controllers/apps/v2beta1/sync_sets_suite_test.go b/controllers/apps/v2beta1/sync_sets_suite_test.go
index 6cc97a51b..9689bf7cb 100644
--- a/controllers/apps/v2beta1/sync_sets_suite_test.go
+++ b/controllers/apps/v2beta1/sync_sets_suite_test.go
@@ -17,7 +17,7 @@ import (
 	"sigs.k8s.io/controller-runtime/pkg/client"
 )
 
-var _ = Describe("Check sync rs", func() {
+var _ = Describe("Check sync sts and pvc", func() {
 	var s *syncSets
 
 	var instance *appsv2beta1.EMQX = new(appsv2beta1.EMQX)