diff --git a/pkg/apis/networking/validation/validation_test.go b/pkg/apis/networking/validation/validation_test.go
index 0599dc299f6..43a48de45e6 100644
--- a/pkg/apis/networking/validation/validation_test.go
+++ b/pkg/apis/networking/validation/validation_test.go
@@ -1663,6 +1663,23 @@ func TestValidateIngressUpdate(t *testing.T) {
 			},
 			expectedErrs: field.ErrorList{field.Invalid(field.NewPath("spec").Child("rules").Index(0).Child("http").Child("paths").Index(0).Child("backend").Child("service").Child("name"), "1-test-service", `a DNS-1035 label must consist of lower case alphanumeric characters or '-', start with an alphabetic character, and end with an alphanumeric character (e.g. 'my-name',  or 'abc-123', regex used for validation is '[a-z]([-a-z0-9]*[a-z0-9])?')`)},
 		},
+		"update defaultBackend service to conform to relaxed service name - RelaxedServiceNameValidation disabled": {
+			tweakIngresses: func(newIngress, oldIngress *networking.Ingress) {
+				oldIngress.Spec.DefaultBackend = &networking.IngressBackend{
+					Service: &networking.IngressServiceBackend{
+						Name: "test-service",
+						Port: networking.ServiceBackendPort{Number: 80},
+					},
+				}
+				newIngress.Spec.DefaultBackend = &networking.IngressBackend{
+					Service: &networking.IngressServiceBackend{
+						Name: "1-test-service",
+						Port: networking.ServiceBackendPort{Number: 80},
+					},
+				}
+			},
+			expectedErrs: field.ErrorList{field.Invalid(field.NewPath("spec").Child("defaultBackend").Child("service").Child("name"), "1-test-service", `a DNS-1035 label must consist of lower case alphanumeric characters or '-', start with an alphabetic character, and end with an alphanumeric character (e.g. 'my-name',  or 'abc-123', regex used for validation is '[a-z]([-a-z0-9]*[a-z0-9])?')`)},
+		},
 		"update service to conform to relaxed service name - RelaxedServiceNameValidation enabled": {
 			tweakIngresses: func(newIngress, oldIngress *networking.Ingress) {
 				oldIngress.Spec.Rules = []networking.IngressRule{{
@@ -1702,6 +1719,23 @@ func TestValidateIngressUpdate(t *testing.T) {
 			},
 			relaxedServiceName: true,
 		},
+		"update defaultBackend service to conform to relaxed service name - RelaxedServiceNameValidation enabled": {
+			tweakIngresses: func(newIngress, oldIngress *networking.Ingress) {
+				oldIngress.Spec.DefaultBackend = &networking.IngressBackend{
+					Service: &networking.IngressServiceBackend{
+						Name: "test-service",
+						Port: networking.ServiceBackendPort{Number: 80},
+					},
+				}
+				newIngress.Spec.DefaultBackend = &networking.IngressBackend{
+					Service: &networking.IngressServiceBackend{
+						Name: "1-test-service",
+						Port: networking.ServiceBackendPort{Number: 80},
+					},
+				}
+			},
+			relaxedServiceName: true,
+		},
 		"updating an already existing relaxed validation service name with RelaxedServiceNameValidation disabled": {
 			tweakIngresses: func(newIngress, oldIngress *networking.Ingress) {
 				oldIngress.Spec.Rules = []networking.IngressRule{{
@@ -1740,6 +1774,22 @@ func TestValidateIngressUpdate(t *testing.T) {
 				}}
 			},
 		},
+		"updating an already existing relaxed validation defaultBackend service name with RelaxedServiceNameValidation disabled": {
+			tweakIngresses: func(newIngress, oldIngress *networking.Ingress) {
+				oldIngress.Spec.DefaultBackend = &networking.IngressBackend{
+					Service: &networking.IngressServiceBackend{
+						Name: "1-test-service",
+						Port: networking.ServiceBackendPort{Number: 80},
+					},
+				}
+				newIngress.Spec.DefaultBackend = &networking.IngressBackend{
+					Service: &networking.IngressServiceBackend{
+						Name: "2-test-service",
+						Port: networking.ServiceBackendPort{Number: 80},
+					},
+				}
+			},
+		},
 		"updating an already existing relaxed validation service name to a non-relaxed name with RelaxedServiceNameValidation disabled": {
 			tweakIngresses: func(newIngress, oldIngress *networking.Ingress) {
 				oldIngress.Spec.Rules = []networking.IngressRule{{
@@ -1778,6 +1828,22 @@ func TestValidateIngressUpdate(t *testing.T) {
 				}}
 			},
 		},
+		"updating an already existing relaxed validation defaultBackend service name to a non-relaxed name with RelaxedServiceNameValidation disabled": {
+			tweakIngresses: func(newIngress, oldIngress *networking.Ingress) {
+				oldIngress.Spec.DefaultBackend = &networking.IngressBackend{
+					Service: &networking.IngressServiceBackend{
+						Name: "1-test-service",
+						Port: networking.ServiceBackendPort{Number: 80},
+					},
+				}
+				newIngress.Spec.DefaultBackend = &networking.IngressBackend{
+					Service: &networking.IngressServiceBackend{
+						Name: "test-service",
+						Port: networking.ServiceBackendPort{Number: 80},
+					},
+				}
+			},
+		},
 	}
 
 	for name, testCase := range testCases {