diff --git a/service/token.go b/service/token.go
index 2497718..638539f 100644
--- a/service/token.go
+++ b/service/token.go
@@ -6,6 +6,7 @@ import (
 	"io"
 
 	"github.com/nspcc-dev/neofs-api-go/refs"
+	crypto "github.com/nspcc-dev/neofs-crypto"
 )
 
 type signAccumWithToken struct {
@@ -125,10 +126,14 @@ func (x Token_Info_Verb) Bytes() []byte {
 	return data
 }
 
-// AddSignKey calls a Signature field setter of token with passed signature.
-func (s signedSessionToken) AddSignKey(sig []byte, _ *ecdsa.PublicKey) {
+// AddSignKey calls a Signature field setter and an OwnerKey field setter with corresponding arguments.
+func (s signedSessionToken) AddSignKey(sig []byte, key *ecdsa.PublicKey) {
 	if s.SessionToken != nil {
 		s.SessionToken.SetSignature(sig)
+
+		s.SessionToken.SetOwnerKey(
+			crypto.MarshalPublicKey(key),
+		)
 	}
 }
 
diff --git a/service/token_test.go b/service/token_test.go
index e8599e7..4fb430a 100644
--- a/service/token_test.go
+++ b/service/token_test.go
@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/nspcc-dev/neofs-api-go/refs"
+	crypto "github.com/nspcc-dev/neofs-crypto"
 	"github.com/nspcc-dev/neofs-crypto/test"
 	"github.com/stretchr/testify/require"
 )
@@ -220,3 +221,28 @@ func TestSignToken(t *testing.T) {
 		require.NoError(t, VerifySignatureWithKey(pk, verifiedToken))
 	}
 }
+
+func TestSignedSessionToken_AddSignKey(t *testing.T) {
+	// nil SessionToken
+	s := new(signedSessionToken)
+
+	require.NotPanics(t, func() {
+		s.AddSignKey(nil, nil)
+	})
+
+	// create test public key and signature
+	pk := &test.DecodeKey(0).PublicKey
+	sig := []byte{1, 2, 3}
+
+	s.SessionToken = new(Token)
+
+	// add key-signature pair to SessionToken
+	s.AddSignKey(sig, pk)
+
+	require.Equal(t, sig, s.GetSignature())
+
+	require.Equal(t,
+		crypto.MarshalPublicKey(pk),
+		s.GetOwnerKey(),
+	)
+}