diff --git a/pkg/services/accounting/sign.go b/pkg/services/accounting/sign.go
index 85a0fb7f1..f3545e7e6 100644
--- a/pkg/services/accounting/sign.go
+++ b/pkg/services/accounting/sign.go
@@ -23,7 +23,7 @@ func NewSignService(key *ecdsa.PrivateKey, svc accounting.Service) accounting.Se
 
 func (s *signService) Balance(ctx context.Context, req *accounting.BalanceRequest) (*accounting.BalanceResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.Balance(ctx, req.(*accounting.BalanceRequest))
 		},
 	)
diff --git a/pkg/services/container/sign.go b/pkg/services/container/sign.go
index 6890de925..f8a4700f2 100644
--- a/pkg/services/container/sign.go
+++ b/pkg/services/container/sign.go
@@ -23,7 +23,7 @@ func NewSignService(key *ecdsa.PrivateKey, svc container.Service) container.Serv
 
 func (s *signService) Put(ctx context.Context, req *container.PutRequest) (*container.PutResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.Put(ctx, req.(*container.PutRequest))
 		},
 	)
@@ -36,7 +36,7 @@ func (s *signService) Put(ctx context.Context, req *container.PutRequest) (*cont
 
 func (s *signService) Delete(ctx context.Context, req *container.DeleteRequest) (*container.DeleteResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.Delete(ctx, req.(*container.DeleteRequest))
 		},
 	)
@@ -49,7 +49,7 @@ func (s *signService) Delete(ctx context.Context, req *container.DeleteRequest)
 
 func (s *signService) Get(ctx context.Context, req *container.GetRequest) (*container.GetResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.Get(ctx, req.(*container.GetRequest))
 		},
 	)
@@ -62,7 +62,7 @@ func (s *signService) Get(ctx context.Context, req *container.GetRequest) (*cont
 
 func (s *signService) List(ctx context.Context, req *container.ListRequest) (*container.ListResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.List(ctx, req.(*container.ListRequest))
 		},
 	)
@@ -75,7 +75,7 @@ func (s *signService) List(ctx context.Context, req *container.ListRequest) (*co
 
 func (s *signService) SetExtendedACL(ctx context.Context, req *container.SetExtendedACLRequest) (*container.SetExtendedACLResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.SetExtendedACL(ctx, req.(*container.SetExtendedACLRequest))
 		},
 	)
@@ -88,7 +88,7 @@ func (s *signService) SetExtendedACL(ctx context.Context, req *container.SetExte
 
 func (s *signService) GetExtendedACL(ctx context.Context, req *container.GetExtendedACLRequest) (*container.GetExtendedACLResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.GetExtendedACL(ctx, req.(*container.GetExtendedACLRequest))
 		},
 	)
diff --git a/pkg/services/netmap/sign.go b/pkg/services/netmap/sign.go
index 57018c41f..0eef0d812 100644
--- a/pkg/services/netmap/sign.go
+++ b/pkg/services/netmap/sign.go
@@ -26,7 +26,7 @@ func (s *signService) LocalNodeInfo(
 	req *netmap.LocalNodeInfoRequest) (*netmap.LocalNodeInfoResponse, error) {
 
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.LocalNodeInfo(ctx, req.(*netmap.LocalNodeInfoRequest))
 		},
 	)
diff --git a/pkg/services/object/sign.go b/pkg/services/object/sign.go
index 95decd048..908d3c031 100644
--- a/pkg/services/object/sign.go
+++ b/pkg/services/object/sign.go
@@ -58,7 +58,7 @@ func (s *signService) Get(ctx context.Context, req *object.GetRequest) (object.G
 				return nil, err
 			}
 
-			return func() (interface{}, error) {
+			return func() (util.ResponseMessage, error) {
 				return stream.Recv()
 			}, nil
 		},
@@ -96,7 +96,7 @@ func (s *signService) Put(ctx context.Context) (object.PutObjectStreamer, error)
 			func(req interface{}) error {
 				return stream.Send(req.(*object.PutRequest))
 			},
-			func() (interface{}, error) {
+			func() (util.ResponseMessage, error) {
 				return stream.CloseAndRecv()
 			},
 		),
@@ -105,7 +105,7 @@ func (s *signService) Put(ctx context.Context) (object.PutObjectStreamer, error)
 
 func (s *signService) Head(ctx context.Context, req *object.HeadRequest) (*object.HeadResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.Head(ctx, req.(*object.HeadRequest))
 		},
 	)
@@ -133,7 +133,7 @@ func (s *signService) Search(ctx context.Context, req *object.SearchRequest) (ob
 				return nil, err
 			}
 
-			return func() (interface{}, error) {
+			return func() (util.ResponseMessage, error) {
 				return stream.Recv()
 			}, nil
 		},
@@ -149,7 +149,7 @@ func (s *signService) Search(ctx context.Context, req *object.SearchRequest) (ob
 
 func (s *signService) Delete(ctx context.Context, req *object.DeleteRequest) (*object.DeleteResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.Delete(ctx, req.(*object.DeleteRequest))
 		},
 	)
@@ -177,7 +177,7 @@ func (s *signService) GetRange(ctx context.Context, req *object.GetRangeRequest)
 				return nil, err
 			}
 
-			return func() (interface{}, error) {
+			return func() (util.ResponseMessage, error) {
 				return stream.Recv()
 			}, nil
 		},
@@ -193,7 +193,7 @@ func (s *signService) GetRange(ctx context.Context, req *object.GetRangeRequest)
 
 func (s *signService) GetRangeHash(ctx context.Context, req *object.GetRangeHashRequest) (*object.GetRangeHashResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.GetRangeHash(ctx, req.(*object.GetRangeHashRequest))
 		},
 	)
diff --git a/pkg/services/session/sign.go b/pkg/services/session/sign.go
index c7dd98a10..c318b1b9d 100644
--- a/pkg/services/session/sign.go
+++ b/pkg/services/session/sign.go
@@ -23,7 +23,7 @@ func NewSignService(key *ecdsa.PrivateKey, svc session.Service) session.Service
 
 func (s *signService) Create(ctx context.Context, req *session.CreateRequest) (*session.CreateResponse, error) {
 	resp, err := s.sigSvc.HandleUnaryRequest(ctx, req,
-		func(ctx context.Context, req interface{}) (interface{}, error) {
+		func(ctx context.Context, req interface{}) (util.ResponseMessage, error) {
 			return s.svc.Create(ctx, req.(*session.CreateRequest))
 		},
 	)
diff --git a/pkg/services/util/sign.go b/pkg/services/util/sign.go
index 0ff416dc0..6264e4f77 100644
--- a/pkg/services/util/sign.go
+++ b/pkg/services/util/sign.go
@@ -8,7 +8,10 @@ import (
 	"github.com/pkg/errors"
 )
 
-type UnaryHandler func(context.Context, interface{}) (interface{}, error)
+// ResponseMessage is an interface of NeoFS response message.
+type ResponseMessage interface{}
+
+type UnaryHandler func(context.Context, interface{}) (ResponseMessage, error)
 
 type SignService struct {
 	key *ecdsa.PrivateKey
@@ -16,7 +19,7 @@ type SignService struct {
 
 type ServerStreamHandler func(context.Context, interface{}) (ResponseMessageReader, error)
 
-type ResponseMessageReader func() (interface{}, error)
+type ResponseMessageReader func() (ResponseMessage, error)
 
 type ResponseMessageStreamer struct {
 	key *ecdsa.PrivateKey
@@ -26,7 +29,7 @@ type ResponseMessageStreamer struct {
 
 type RequestMessageWriter func(interface{}) error
 
-type ClientStreamCloser func() (interface{}, error)
+type ClientStreamCloser func() (ResponseMessage, error)
 
 type RequestMessageStreamer struct {
 	key *ecdsa.PrivateKey