diff --git a/admission/cocoonhibernation_validator.go b/admission/cocoonhibernation_validator.go
index 87ecd64..a81f9cb 100644
--- a/admission/cocoonhibernation_validator.go
+++ b/admission/cocoonhibernation_validator.go
@@ -35,6 +35,13 @@ func (s *Server) validateCocoonHibernation(ctx context.Context, review *admissio
 		return recordDeny(metrics.HandlerValidateHibernation, metrics.ResultError, metrics.ReasonDecode, fmt.Sprintf("decode CocoonHibernation: %v", err))
 	}
 
+	if !hib.Spec.Desire.IsValid() {
+		msg := fmt.Sprintf("cocoon-webhook: spec.desire must be %s or %s, got %q",
+			cocoonv1.HibernationDesireHibernate, cocoonv1.HibernationDesireWake, hib.Spec.Desire)
+		logger.Warnf(ctx, "validate %s/%s DENY: %s", req.Namespace, req.Name, msg)
+		return recordDeny(metrics.HandlerValidateHibernation, metrics.ResultDeny, "", msg)
+	}
+
 	if hib.Name != hib.Spec.PodRef.Name {
 		msg := fmt.Sprintf("cocoon-webhook: metadata.name %q must equal spec.podRef.name %q (one CocoonHibernation per pod, named after it)",
 			hib.Name, hib.Spec.PodRef.Name)
diff --git a/admission/cocoonhibernation_validator_test.go b/admission/cocoonhibernation_validator_test.go
index 0174083..80c445d 100644
--- a/admission/cocoonhibernation_validator_test.go
+++ b/admission/cocoonhibernation_validator_test.go
@@ -49,6 +49,31 @@ func TestValidateCocoonHibernationRejectsTerminatingPredecessor(t *testing.T) {
 	}
 }
 
+func TestValidateCocoonHibernationRejectsInvalidDesire(t *testing.T) {
+	srv := newHibernationServer(t)
+	hib := hibernation("pod-a", "pod-a", nil)
+	hib.Spec.Desire = "Sleep"
+	raw, err := json.Marshal(hib)
+	if err != nil {
+		t.Fatalf("marshal: %v", err)
+	}
+	resp := srv.validateCocoonHibernation(t.Context(), &admissionv1.AdmissionReview{
+		Request: &admissionv1.AdmissionRequest{
+			UID:       "uid",
+			Namespace: "ns",
+			Name:      "pod-a",
+			Operation: admissionv1.Create,
+			Object:    runtime.RawExtension{Raw: raw},
+		},
+	})
+	if resp.Allowed {
+		t.Fatalf("invalid spec.desire should be denied")
+	}
+	if !strings.Contains(resp.Result.Message, "spec.desire") {
+		t.Errorf("denial should name spec.desire, got %q", resp.Result.Message)
+	}
+}
+
 func TestValidateCocoonHibernationAllowsDistinctPods(t *testing.T) {
 	srv := newHibernationServer(t, hibernation("legacy-name", "pod-a", nil))
 	resp := srv.validateCocoonHibernation(t.Context(), hibernationReview(t, admissionv1.Create, "pod-b", "pod-b"))
diff --git a/go.mod b/go.mod
index 547bc22..21f491b 100644
--- a/go.mod
+++ b/go.mod
@@ -3,7 +3,7 @@ module github.com/cocoonstack/cocoon-webhook
 go 1.26.5
 
 require (
-	github.com/cocoonstack/cocoon-common v0.2.8-0.20260724145826-4363e4ff03ee
+	github.com/cocoonstack/cocoon-common v0.2.8-0.20260726095001-32dacef3f4c1
 	github.com/projecteru2/core v0.0.0-20241016125006-ff909eefe04c
 	github.com/prometheus/client_golang v1.23.2
 	github.com/prometheus/client_model v0.6.2
diff --git a/go.sum b/go.sum
index 69fd193..a83d615 100644
--- a/go.sum
+++ b/go.sum
@@ -27,8 +27,8 @@ github.com/cockroachdb/logtags v0.0.0-20230118201751-21c54148d20b h1:r6VH0faHjZe
 github.com/cockroachdb/logtags v0.0.0-20230118201751-21c54148d20b/go.mod h1:Vz9DsVWQQhf3vs21MhPMZpMGSht7O/2vFW2xusFUVOs=
 github.com/cockroachdb/redact v1.1.3 h1:AKZds10rFSIj7qADf0g46UixK8NNLwWTNdCIGS5wfSQ=
 github.com/cockroachdb/redact v1.1.3/go.mod h1:BVNblN9mBWFyMyqK1k3AAiSxhvhfK2oOZZ2lK+dpvRg=
-github.com/cocoonstack/cocoon-common v0.2.8-0.20260724145826-4363e4ff03ee h1:KshBIXkOlQMNdL7DPoYXitxq+qeWyQSqQsvIpDV0gv4=
-github.com/cocoonstack/cocoon-common v0.2.8-0.20260724145826-4363e4ff03ee/go.mod h1:VSfgYiWxoHRnWybzQNaxmK4kVoLT9ffiMKll5/i92CM=
+github.com/cocoonstack/cocoon-common v0.2.8-0.20260726095001-32dacef3f4c1 h1:JTQr97YGwJ71druXkVHYb6m1HIIzY/J3pputWAeYHUM=
+github.com/cocoonstack/cocoon-common v0.2.8-0.20260726095001-32dacef3f4c1/go.mod h1:VSfgYiWxoHRnWybzQNaxmK4kVoLT9ffiMKll5/i92CM=
 github.com/codegangsta/inject v0.0.0-20150114235600-33e0aa1cb7c0/go.mod h1:4Zcjuz89kmFXt9morQgcfYZAYZ5n8WHjt81YYWIwtTM=
 github.com/coreos/etcd v3.3.10+incompatible/go.mod h1:uF7uidLiAD3TWHmW31ZFd/JWoc32PjwdhPthX9715RE=
 github.com/coreos/go-etcd v2.0.0+incompatible/go.mod h1:Jez6KQU2B/sWsbdaef3ED8NzMklzPG4d5KIOhIy30Tk=