diff --git a/pkg/apis/core/v1/zz_generated.defaults.go b/pkg/apis/core/v1/zz_generated.defaults.go
index 2863cc3ab8f..493d9903e1b 100644
--- a/pkg/apis/core/v1/zz_generated.defaults.go
+++ b/pkg/apis/core/v1/zz_generated.defaults.go
@@ -913,6 +913,12 @@ func SetObjectDefaults_SecretList(in *v1.SecretList) {
 
 func SetObjectDefaults_Service(in *v1.Service) {
 	SetDefaults_Service(in)
+	for i := range in.Spec.Ports {
+		a := &in.Spec.Ports[i]
+		if a.Protocol == "" {
+			a.Protocol = "TCP"
+		}
+	}
 }
 
 func SetObjectDefaults_ServiceList(in *v1.ServiceList) {
diff --git a/staging/src/k8s.io/api/core/v1/generated.proto b/staging/src/k8s.io/api/core/v1/generated.proto
index 386e4bdb461..742602b2db6 100644
--- a/staging/src/k8s.io/api/core/v1/generated.proto
+++ b/staging/src/k8s.io/api/core/v1/generated.proto
@@ -4751,6 +4751,7 @@ message ServicePort {
 
   // The IP protocol for this port. Supports "TCP", "UDP", and "SCTP".
   // Default is TCP.
+  // +default="TCP"
   // +optional
   optional string protocol = 2;
 
diff --git a/staging/src/k8s.io/api/core/v1/types.go b/staging/src/k8s.io/api/core/v1/types.go
index 6465fc53959..59feb2d74ad 100644
--- a/staging/src/k8s.io/api/core/v1/types.go
+++ b/staging/src/k8s.io/api/core/v1/types.go
@@ -4265,6 +4265,7 @@ type ServicePort struct {
 
 	// The IP protocol for this port. Supports "TCP", "UDP", and "SCTP".
 	// Default is TCP.
+	// +default="TCP"
 	// +optional
 	Protocol Protocol `json:"protocol,omitempty" protobuf:"bytes,2,opt,name=protocol,casttype=Protocol"`