diff --git a/api/openapi-spec/swagger.json b/api/openapi-spec/swagger.json
index 9517af44c8d..a8c875feda1 100644
--- a/api/openapi-spec/swagger.json
+++ b/api/openapi-spec/swagger.json
@@ -20607,7 +20607,6 @@
         }
       },
       "required": [
-        "service",
         "groupPriorityMinimum",
         "versionPriority"
       ],
@@ -20778,7 +20777,6 @@
         }
       },
       "required": [
-        "service",
         "groupPriorityMinimum",
         "versionPriority"
       ],
diff --git a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/types.go b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/types.go
index 76581596d52..1fd9780bba4 100644
--- a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/types.go
+++ b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/types.go
@@ -48,6 +48,7 @@ type APIServiceSpec struct {
 	// on port 443
 	// If the Service is nil, that means the handling for the API groupversion is handled locally on this server.
 	// The call will simply delegate to the normal handler chain to be fulfilled.
+	// +optional
 	Service *ServiceReference
 	// Group is the API group name this server hosts
 	Group string
diff --git a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1/generated.proto b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1/generated.proto
index 6dd1f270581..4cc3b3b168a 100644
--- a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1/generated.proto
+++ b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1/generated.proto
@@ -76,6 +76,7 @@ message APIServiceSpec {
   // on port 443
   // If the Service is nil, that means the handling for the API groupversion is handled locally on this server.
   // The call will simply delegate to the normal handler chain to be fulfilled.
+  // +optional
   optional ServiceReference service = 1;
 
   // Group is the API group name this server hosts
diff --git a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1/types.go b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1/types.go
index f445410ffbd..38607dfe7d5 100644
--- a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1/types.go
+++ b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1/types.go
@@ -48,7 +48,8 @@ type APIServiceSpec struct {
 	// on port 443
 	// If the Service is nil, that means the handling for the API groupversion is handled locally on this server.
 	// The call will simply delegate to the normal handler chain to be fulfilled.
-	Service *ServiceReference `json:"service" protobuf:"bytes,1,opt,name=service"`
+	// +optional
+	Service *ServiceReference `json:"service,omitempty" protobuf:"bytes,1,opt,name=service"`
 	// Group is the API group name this server hosts
 	Group string `json:"group,omitempty" protobuf:"bytes,2,opt,name=group"`
 	// Version is the API version this server hosts.  For example, "v1"
diff --git a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1beta1/generated.proto b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1beta1/generated.proto
index a8e329f8187..4e78358e437 100644
--- a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1beta1/generated.proto
+++ b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1beta1/generated.proto
@@ -76,6 +76,7 @@ message APIServiceSpec {
   // on port 443
   // If the Service is nil, that means the handling for the API groupversion is handled locally on this server.
   // The call will simply delegate to the normal handler chain to be fulfilled.
+  // +optional
   optional ServiceReference service = 1;
 
   // Group is the API group name this server hosts
diff --git a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1beta1/types.go b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1beta1/types.go
index 91ce0a1dc8d..33731c3b362 100644
--- a/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1beta1/types.go
+++ b/staging/src/k8s.io/kube-aggregator/pkg/apis/apiregistration/v1beta1/types.go
@@ -48,7 +48,8 @@ type APIServiceSpec struct {
 	// on port 443
 	// If the Service is nil, that means the handling for the API groupversion is handled locally on this server.
 	// The call will simply delegate to the normal handler chain to be fulfilled.
-	Service *ServiceReference `json:"service" protobuf:"bytes,1,opt,name=service"`
+	// +optional
+	Service *ServiceReference `json:"service,omitempty" protobuf:"bytes,1,opt,name=service"`
 	// Group is the API group name this server hosts
 	Group string `json:"group,omitempty" protobuf:"bytes,2,opt,name=group"`
 	// Version is the API version this server hosts.  For example, "v1"