diff --git a/pkg/webhook/handlers/validation.go b/pkg/webhook/handlers/validation.go
index 9406605e4..dce77bcbd 100644
--- a/pkg/webhook/handlers/validation.go
+++ b/pkg/webhook/handlers/validation.go
@@ -74,17 +74,26 @@ func (r *registryBackedValidator) Validate(admissionSpec *admissionv1beta1.Admis
 		}
 	}
 
-	requestGVK := schema.GroupVersionKind{
-		Group:   admissionSpec.RequestKind.Group,
-		Version: admissionSpec.RequestKind.Version,
-		Kind:    admissionSpec.RequestKind.Kind,
+	// RequestKind field is only present from Kubernetes 1.15 onwards, so
+	// use the regular 'kind' if RequestKind is not present
+	gvk := schema.GroupVersionKind{
+		Group:   admissionSpec.Kind.Group,
+		Version: admissionSpec.Kind.Version,
+		Kind:    admissionSpec.Kind.Kind,
+	}
+	if admissionSpec.RequestKind != nil {
+		gvk = schema.GroupVersionKind{
+			Group:   admissionSpec.RequestKind.Group,
+			Version: admissionSpec.RequestKind.Version,
+			Kind:    admissionSpec.RequestKind.Kind,
+		}
 	}
 	errs := field.ErrorList{}
 	// perform validation on new version of resource
-	errs = append(errs, r.registry.Validate(obj, requestGVK)...)
+	errs = append(errs, r.registry.Validate(obj, gvk)...)
 	if oldObj != nil {
 		// perform update validation on resource
-		errs = append(errs, r.registry.ValidateUpdate(oldObj, obj, requestGVK)...)
+		errs = append(errs, r.registry.ValidateUpdate(oldObj, obj, gvk)...)
 	}
 	// return with allowed = false if any errors occurred
 	if err := errs.ToAggregate(); err != nil {
diff --git a/pkg/webhook/handlers/validation_test.go b/pkg/webhook/handlers/validation_test.go
index 16d5a1d99..cf512a743 100644
--- a/pkg/webhook/handlers/validation_test.go
+++ b/pkg/webhook/handlers/validation_test.go
@@ -247,6 +247,34 @@ func TestRegistryBackedValidator(t *testing.T) {
 				Allowed: true,
 			},
 		},
+		"should validate in the current APIVersion if RequestKind is not set (for Kubernetes <1.15 support)": {
+			inputRequest: admissionv1beta1.AdmissionRequest{
+				UID:  types.UID("abc"),
+				Kind: *testTypeGVKV2,
+				Object: runtime.RawExtension{
+					Raw: []byte(fmt.Sprintf(`
+{
+	"apiVersion": "testgroup.testing.cert-manager.io/v2",
+	"kind": "TestType",
+	"metadata": {
+		"name": "testing",
+		"namespace": "abc",
+		"creationTimestamp": null
+	},
+	"testField": "%s"
+}
+`, v2.DisallowedTestFieldValue)),
+				},
+			},
+			expectedResponse: admissionv1beta1.AdmissionResponse{
+				UID:     types.UID("abc"),
+				Allowed: false,
+				Result: &metav1.Status{
+					Status: metav1.StatusFailure, Code: http.StatusNotAcceptable, Reason: metav1.StatusReasonNotAcceptable,
+					Message: "testField: Invalid value: \"not-allowed-in-v2\": value not allowed",
+				},
+			},
+		},
 	}
 
 	for n, test := range tests {