diff --git a/go.mod b/go.mod
index bc1f84d..e7cacce 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,6 @@ module github.com/unistack-org/micro-codec-proto/v3
 go 1.16
 
 require (
-	github.com/unistack-org/micro/v3 v3.3.17
+	github.com/unistack-org/micro/v3 v3.3.19
 	google.golang.org/protobuf v1.26.0
 )
diff --git a/go.sum b/go.sum
index cb3cb20..aba4cb4 100644
--- a/go.sum
+++ b/go.sum
@@ -7,9 +7,9 @@ github.com/google/uuid v1.2.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+
 github.com/imdario/mergo v0.3.12/go.mod h1:jmQim1M+e3UYxmgPu/WyfjB3N3VflVyUjjjwH0dnCYA=
 github.com/patrickmn/go-cache v2.1.0+incompatible/go.mod h1:3Qf8kWWT7OJRJbdiICTKqZju1ZixQ/KpMGzzAfe6+WQ=
 github.com/silas/dag v0.0.0-20210121180416-41cf55125c34/go.mod h1:7RTUFBdIRC9nZ7/3RyRNH1bdqIShrDejd1YbLwgPS+I=
-github.com/unistack-org/micro/v3 v3.3.17 h1:WcyS7InP0DlS/JpRQGLh5sG6VstkdHJbgpMp+gmHmwg=
-github.com/unistack-org/micro/v3 v3.3.17/go.mod h1:022EOEZZ789hZY3yB5ZSMXU6jLiadBgcNB/cpediV3c=
-golang.org/x/net v0.0.0-20210423184538-5f58ad60dda6/go.mod h1:OJAsFXCWl8Ukc7SiCT/9KSuxbyM7479/AVlXFRxuMCk=
+github.com/unistack-org/micro/v3 v3.3.19 h1:x0bl4H+IZvdHHKfA8qMcox9W92+e7rtbqgRfQPoP79w=
+github.com/unistack-org/micro/v3 v3.3.19/go.mod h1:LXmPfbJnJNvL0kQs8HfnkV3Wya2Wb+C7keVq++RCZnk=
+golang.org/x/net v0.0.0-20210510120150-4163338589ed/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
diff --git a/proto.go b/proto.go
index 86b0031..88f6e0b 100644
--- a/proto.go
+++ b/proto.go
@@ -3,14 +3,18 @@ package proto
 
 import (
 	"io"
-	"io/ioutil"
 
 	"github.com/unistack-org/micro/v3/codec"
+	rutil "github.com/unistack-org/micro/v3/util/reflect"
 	"google.golang.org/protobuf/proto"
 )
 
 type protoCodec struct{}
 
+const (
+	flattenTag = "flatten"
+)
+
 func (c *protoCodec) Marshal(v interface{}) ([]byte, error) {
 	switch m := v.(type) {
 	case nil:
@@ -18,6 +22,11 @@ func (c *protoCodec) Marshal(v interface{}) ([]byte, error) {
 	case *codec.Frame:
 		return m.Data, nil
 	case proto.Message:
+		if nv, nerr := rutil.StructFieldByTag(v, codec.DefaultTagName, flattenTag); nerr == nil {
+			if nm, ok := nv.(proto.Message); ok {
+				return proto.Marshal(nm)
+			}
+		}
 		return proto.Marshal(m)
 	}
 	return nil, codec.ErrInvalidMessage
@@ -33,6 +42,11 @@ func (c *protoCodec) Unmarshal(d []byte, v interface{}) error {
 	case *codec.Frame:
 		m.Data = d
 	case proto.Message:
+		if nv, nerr := rutil.StructFieldByTag(v, codec.DefaultTagName, flattenTag); nerr == nil {
+			if nm, ok := nv.(proto.Message); ok {
+				return proto.Unmarshal(d, nm)
+			}
+		}
 		return proto.Unmarshal(d, m)
 	}
 	return codec.ErrInvalidMessage
@@ -42,12 +56,12 @@ func (c *protoCodec) ReadHeader(conn io.Reader, m *codec.Message, t codec.Messag
 	return nil
 }
 
-func (c *protoCodec) ReadBody(conn io.Reader, b interface{}) error {
-	switch m := b.(type) {
+func (c *protoCodec) ReadBody(conn io.Reader, v interface{}) error {
+	switch m := v.(type) {
 	case nil:
 		return nil
 	case *codec.Frame:
-		buf, err := ioutil.ReadAll(conn)
+		buf, err := io.ReadAll(conn)
 		if err != nil {
 			return err
 		} else if len(buf) == 0 {
@@ -56,28 +70,45 @@ func (c *protoCodec) ReadBody(conn io.Reader, b interface{}) error {
 		m.Data = buf
 		return nil
 	case proto.Message:
-		buf, err := ioutil.ReadAll(conn)
+		buf, err := io.ReadAll(conn)
 		if err != nil {
 			return err
 		} else if len(buf) == 0 {
 			return nil
 		}
+		if nv, nerr := rutil.StructFieldByTag(v, codec.DefaultTagName, flattenTag); nerr == nil {
+			if nm, ok := nv.(proto.Message); ok {
+				return proto.Unmarshal(buf, nm)
+			}
+		}
 		return proto.Unmarshal(buf, m)
 	}
 	return codec.ErrInvalidMessage
 }
 
-func (c *protoCodec) Write(conn io.Writer, m *codec.Message, b interface{}) error {
-	switch m := b.(type) {
+func (c *protoCodec) Write(conn io.Writer, m *codec.Message, v interface{}) error {
+	switch m := v.(type) {
 	case nil:
 		return nil
 	case *codec.Frame:
 		_, err := conn.Write(m.Data)
 		return err
 	case proto.Message:
-		buf, err := proto.Marshal(m)
+		var buf []byte
+		var err error
+
+		if nv, nerr := rutil.StructFieldByTag(v, codec.DefaultTagName, flattenTag); nerr == nil {
+			if nm, ok := nv.(proto.Message); ok {
+				buf, err = proto.Marshal(nm)
+			}
+		} else {
+			buf, err = proto.Marshal(m)
+		}
+
 		if err != nil {
 			return err
+		} else if len(buf) == 0 {
+			return codec.ErrInvalidMessage
 		}
 		_, err = conn.Write(buf)
 		return err