diff --git a/coordinator/coordapi_test.go b/coordinator/coordapi_test.go
index a4194ede1..c31bb4bee 100644
--- a/coordinator/coordapi_test.go
+++ b/coordinator/coordapi_test.go
@@ -2,6 +2,12 @@ package main
 
 import (
 	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
 	"encoding/json"
 	"log/slog"
 	"sync"
@@ -13,6 +19,8 @@ import (
 	"github.com/edgelesssys/nunki/internal/memstore"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/peer"
 )
 
 func TestManifestSet(t *testing.T) {
@@ -28,12 +36,21 @@ func TestManifestSet(t *testing.T) {
 		require.NoError(t, err)
 		return b
 	}
+	trustedKey, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
+	require.NoError(t, err)
+	untrustedKey, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
+	require.NoError(t, err)
+	manifestWithTrustedKey, err := manifestWithWorkloadOwnerKey(trustedKey)
+	require.NoError(t, err)
+	manifestWithoutTrustedKey, err := manifestWithWorkloadOwnerKey(nil)
+	require.NoError(t, err)
 
 	testCases := map[string]struct {
-		req      *coordapi.SetManifestRequest
-		mSGetter *stubManifestSetGetter
-		caGetter *stubCertChainGetter
-		wantErr  bool
+		req              *coordapi.SetManifestRequest
+		mSGetter         *stubManifestSetGetter
+		caGetter         *stubCertChainGetter
+		workloadOwnerKey *ecdsa.PrivateKey
+		wantErr          bool
 	}{
 		"empty request": {
 			req:      &coordapi.SetManifestRequest{},
@@ -110,6 +127,84 @@ func TestManifestSet(t *testing.T) {
 			caGetter: &stubCertChainGetter{},
 			wantErr:  true,
 		},
+		"workload owner key match": {
+			req: &coordapi.SetManifestRequest{
+				Manifest: newManifestBytes(func(m *manifest.Manifest) {
+					m.Policies = map[manifest.HexString][]string{
+						manifest.HexString("ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb"): {"a1", "a2"},
+						manifest.HexString("3e23e8160039594a33894f6564e1b1348bbd7a0088d42c4acb73eeaed59c009d"): {"b1", "b2"},
+					}
+				}),
+				Policies: [][]byte{
+					[]byte("a"),
+					[]byte("b"),
+				},
+			},
+			mSGetter: &stubManifestSetGetter{
+				getManifestResp: []*manifest.Manifest{manifestWithTrustedKey},
+			},
+			caGetter:         &stubCertChainGetter{},
+			workloadOwnerKey: trustedKey,
+		},
+		"workload owner key mismatch": {
+			req: &coordapi.SetManifestRequest{
+				Manifest: newManifestBytes(func(m *manifest.Manifest) {
+					m.Policies = map[manifest.HexString][]string{
+						manifest.HexString("ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb"): {"a1", "a2"},
+						manifest.HexString("3e23e8160039594a33894f6564e1b1348bbd7a0088d42c4acb73eeaed59c009d"): {"b1", "b2"},
+					}
+				}),
+				Policies: [][]byte{
+					[]byte("a"),
+					[]byte("b"),
+				},
+			},
+			mSGetter: &stubManifestSetGetter{
+				getManifestResp: []*manifest.Manifest{manifestWithTrustedKey},
+			},
+			caGetter:         &stubCertChainGetter{},
+			workloadOwnerKey: untrustedKey,
+			wantErr:          true,
+		},
+		"workload owner key missing": {
+			req: &coordapi.SetManifestRequest{
+				Manifest: newManifestBytes(func(m *manifest.Manifest) {
+					m.Policies = map[manifest.HexString][]string{
+						manifest.HexString("ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb"): {"a1", "a2"},
+						manifest.HexString("3e23e8160039594a33894f6564e1b1348bbd7a0088d42c4acb73eeaed59c009d"): {"b1", "b2"},
+					}
+				}),
+				Policies: [][]byte{
+					[]byte("a"),
+					[]byte("b"),
+				},
+			},
+			mSGetter: &stubManifestSetGetter{
+				getManifestResp: []*manifest.Manifest{manifestWithTrustedKey},
+			},
+			caGetter: &stubCertChainGetter{},
+			wantErr:  true,
+		},
+		"manifest not updatable": {
+			req: &coordapi.SetManifestRequest{
+				Manifest: newManifestBytes(func(m *manifest.Manifest) {
+					m.Policies = map[manifest.HexString][]string{
+						manifest.HexString("ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb"): {"a1", "a2"},
+						manifest.HexString("3e23e8160039594a33894f6564e1b1348bbd7a0088d42c4acb73eeaed59c009d"): {"b1", "b2"},
+					}
+				}),
+				Policies: [][]byte{
+					[]byte("a"),
+					[]byte("b"),
+				},
+			},
+			mSGetter: &stubManifestSetGetter{
+				getManifestResp: []*manifest.Manifest{manifestWithoutTrustedKey},
+			},
+			caGetter:         &stubCertChainGetter{},
+			workloadOwnerKey: trustedKey,
+			wantErr:          true,
+		},
 	}
 
 	for name, tc := range testCases {
@@ -124,7 +219,7 @@ func TestManifestSet(t *testing.T) {
 				logger:          slog.Default(),
 			}
 
-			ctx := context.Background()
+			ctx := rpcContext(tc.workloadOwnerKey)
 			resp, err := coordinator.SetManifest(ctx, tc.req)
 
 			if tc.wantErr {
@@ -303,6 +398,36 @@ func (s *stubCertChainGetter) GetRootCACert() []byte { return []byte("root") }
 func (s *stubCertChainGetter) GetMeshCACert() []byte { return []byte("mesh") }
 func (s *stubCertChainGetter) GetIntermCert() []byte { return []byte("inter") }
 
+func rpcContext(key *ecdsa.PrivateKey) context.Context {
+	var peerCertificates []*x509.Certificate
+	if key != nil {
+		peerCertificates = []*x509.Certificate{{
+			PublicKey:          key.Public(),
+			PublicKeyAlgorithm: x509.ECDSA,
+		}}
+	}
+	return peer.NewContext(context.Background(), &peer.Peer{
+		AuthInfo: credentials.TLSInfo{State: tls.ConnectionState{
+			PeerCertificates: peerCertificates,
+		}},
+	})
+}
+
+func manifestWithWorkloadOwnerKey(key *ecdsa.PrivateKey) (*manifest.Manifest, error) {
+	m := manifest.Default()
+	if key == nil {
+		return &m, nil
+	}
+	pubKey, err := x509.MarshalPKIXPublicKey(&key.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+	ownerKeyHash := sha256.Sum256(pubKey)
+	ownerKeyHex := manifest.NewHexString(ownerKeyHash[:])
+	m.WorkloadOwnerKeyDigests = []manifest.HexString{ownerKeyHex}
+	return &m, nil
+}
+
 func toPtr[T any](t T) *T {
 	return &t
 }