diff --git a/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.json b/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.json
index 82712367889..1aeb652c492 100644
--- a/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.json
+++ b/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.json
@@ -123,7 +123,8 @@
       {
         "expression": "expressionValue",
         "message": "messageValue",
-        "reason": "reasonValue"
+        "reason": "reasonValue",
+        "messageExpression": "messageExpressionValue"
       }
     ],
     "failurePolicy": "failurePolicyValue",
diff --git a/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.pb b/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.pb
index ab0bc7c9350..86a25cb59fa 100644
Binary files a/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.pb and b/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.pb differ
diff --git a/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.yaml b/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.yaml
index a52531b9a00..82207627cd1 100644
--- a/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.yaml
+++ b/staging/src/k8s.io/api/testdata/HEAD/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.yaml
@@ -85,4 +85,5 @@ spec:
   validations:
   - expression: expressionValue
     message: messageValue
+    messageExpression: messageExpressionValue
     reason: reasonValue
diff --git a/staging/src/k8s.io/api/testdata/v1.26.0/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.after_roundtrip.pb b/staging/src/k8s.io/api/testdata/v1.26.0/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.after_roundtrip.pb
new file mode 100644
index 00000000000..b3ff600da14
Binary files /dev/null and b/staging/src/k8s.io/api/testdata/v1.26.0/admissionregistration.k8s.io.v1alpha1.ValidatingAdmissionPolicy.after_roundtrip.pb differ