diff --git a/pkg/apis/apps/types.go b/pkg/apis/apps/types.go
index 8d228de8e4b..a3b7786d462 100644
--- a/pkg/apis/apps/types.go
+++ b/pkg/apis/apps/types.go
@@ -198,6 +198,7 @@ type StatefulSetSpec struct {
 	// the network identity of the set. Pods get DNS/hostnames that follow the
 	// pattern: pod-specific-string.serviceName.default.svc.cluster.local
 	// where "pod-specific-string" is managed by the StatefulSet controller.
+	// +optional
 	ServiceName string
 
 	// PodManagementPolicy controls how pods are created during initial scale up,
diff --git a/staging/src/k8s.io/api/apps/v1/types.go b/staging/src/k8s.io/api/apps/v1/types.go
index 0f4102907ca..7368e8ebb47 100644
--- a/staging/src/k8s.io/api/apps/v1/types.go
+++ b/staging/src/k8s.io/api/apps/v1/types.go
@@ -220,6 +220,7 @@ type StatefulSetSpec struct {
 	// the network identity of the set. Pods get DNS/hostnames that follow the
 	// pattern: pod-specific-string.serviceName.default.svc.cluster.local
 	// where "pod-specific-string" is managed by the StatefulSet controller.
+	// +optional
 	ServiceName string `json:"serviceName" protobuf:"bytes,5,opt,name=serviceName"`
 
 	// podManagementPolicy controls how pods are created during initial scale up,
diff --git a/staging/src/k8s.io/api/apps/v1beta1/types.go b/staging/src/k8s.io/api/apps/v1beta1/types.go
index 85710264fe3..b97a050bfde 100644
--- a/staging/src/k8s.io/api/apps/v1beta1/types.go
+++ b/staging/src/k8s.io/api/apps/v1beta1/types.go
@@ -259,6 +259,7 @@ type StatefulSetSpec struct {
 	// the network identity of the set. Pods get DNS/hostnames that follow the
 	// pattern: pod-specific-string.serviceName.default.svc.cluster.local
 	// where "pod-specific-string" is managed by the StatefulSet controller.
+	// +optional
 	ServiceName string `json:"serviceName" protobuf:"bytes,5,opt,name=serviceName"`
 
 	// podManagementPolicy controls how pods are created during initial scale up,
diff --git a/staging/src/k8s.io/api/apps/v1beta2/types.go b/staging/src/k8s.io/api/apps/v1beta2/types.go
index cc7d6582f50..2d88bfba534 100644
--- a/staging/src/k8s.io/api/apps/v1beta2/types.go
+++ b/staging/src/k8s.io/api/apps/v1beta2/types.go
@@ -269,6 +269,7 @@ type StatefulSetSpec struct {
 	// the network identity of the set. Pods get DNS/hostnames that follow the
 	// pattern: pod-specific-string.serviceName.default.svc.cluster.local
 	// where "pod-specific-string" is managed by the StatefulSet controller.
+	// +optional
 	ServiceName string `json:"serviceName" protobuf:"bytes,5,opt,name=serviceName"`
 
 	// podManagementPolicy controls how pods are created during initial scale up,