diff --git a/api/message/msgpack/codec_test.go b/api/message/msgpack/codec_test.go
index e3dbd1b..787c1e3 100644
--- a/api/message/msgpack/codec_test.go
+++ b/api/message/msgpack/codec_test.go
@@ -39,13 +39,16 @@ func TestMsgpack_EncodeActionTrace(t *testing.T) {
 		Authorization: []message.PermissionLevel{
 			{Actor: "mygame", Permission: "active"},
 		},
+		Except: "errstr",
+		Error:  2,
+		Return: []byte{0xde, 0xad, 0xbe, 0xef},
 	}
 
 	data, err := msgpack.Marshal(msg)
 	assert.NoError(t, err)
 
 	expected := []byte{
-		0x87, 0xa5, 0x74, 0x78, 0x5f, 0x69, 0x64, 0xd9,
+		0x8a, 0xa5, 0x74, 0x78, 0x5f, 0x69, 0x64, 0xd9,
 		0x40, 0x65, 0x64, 0x63, 0x30, 0x36, 0x64, 0x63,
 		0x65, 0x36, 0x33, 0x32, 0x30, 0x34, 0x35, 0x39,
 		0x66, 0x64, 0x36, 0x34, 0x34, 0x37, 0x35, 0x36,
@@ -93,7 +96,11 @@ func TestMsgpack_EncodeActionTrace(t *testing.T) {
 		0x6f, 0x72, 0xa6, 0x6d, 0x79, 0x67, 0x61, 0x6d,
 		0x65, 0xaa, 0x70, 0x65, 0x72, 0x6d, 0x69, 0x73,
 		0x73, 0x69, 0x6f, 0x6e, 0xa6, 0x61, 0x63, 0x74,
-		0x69, 0x76, 0x65,
+		0x69, 0x76, 0x65, 0xa6, 0x65, 0x78, 0x63, 0x65,
+		0x70, 0x74, 0xa6, 0x65, 0x72, 0x72, 0x73, 0x74,
+		0x72, 0xa5, 0x65, 0x72, 0x72, 0x6f, 0x72, 0x02,
+		0xa6, 0x72, 0x65, 0x74, 0x75, 0x72, 0x6e, 0xc4,
+		0x4, 0xde, 0xad, 0xbe, 0xef,
 	}
 
 	assert.Equal(t, expected, data)
@@ -102,7 +109,7 @@ func TestMsgpack_EncodeActionTrace(t *testing.T) {
 func TestMsgpack_Decode(t *testing.T) {
 	RegisterGeneratedResolver()
 
-	data := []byte("\x87\xa5tx_id\xd9@edc06dce6320459fd644756972048da453b2816b0a434c37ddffde36778dcab3\xa4name\xa4drop\xa8contract\xa6mygame\xa8receiver\xa8account1\xa4dataċ{\"dropped_from_id\":674562,\"item\":{\"dur\":145,\"id\":49623,\"name\":\"Shadowmourne\",\"qual\":\"legendary\",\"sta\":198,\"str\":223},\"receiver\":\"account1\"}\xa8hex_data\xda\x01\x167b2264726f707065645f66726f6d5f6964223a3637343536322c226974656d223a7b22647572223a3134352c226964223a34393632332c226e616d65223a22536861646f776d6f75726e65222c227175616c223a226c6567656e64617279222c22737461223a3139382c22737472223a3232337d2c227265636569766572223a226163636f756e7431227d\xadauthorization\x91\x82\xa5actor\xa6mygame\xaapermission\xa6active")
+	data := []byte("\x8a\xa5tx_id\xd9@edc06dce6320459fd644756972048da453b2816b0a434c37ddffde36778dcab3\xa4name\xa4drop\xa8contract\xa6mygame\xa8receiver\xa8account1\xa4dataċ{\"dropped_from_id\":674562,\"item\":{\"dur\":145,\"id\":49623,\"name\":\"Shadowmourne\",\"qual\":\"legendary\",\"sta\":198,\"str\":223},\"receiver\":\"account1\"}\xa8hex_data\xda\x01\x167b2264726f707065645f66726f6d5f6964223a3637343536322c226974656d223a7b22647572223a3134352c226964223a34393632332c226e616d65223a22536861646f776d6f75726e65222c227175616c223a226c6567656e64617279222c22737461223a3139382c22737472223a3232337d2c227265636569766572223a226163636f756e7431227d\xadauthorization\x91\x82\xa5actor\xa6mygame\xaapermission\xa6active\xa6except\xa6errstr\xa5error\x02\xa6return\xc4\x04ޭ\xbe\xef")
 
 	dataJson, err := json.Marshal(map[string]interface{}{
 		"item": map[string]interface{}{
@@ -129,6 +136,9 @@ func TestMsgpack_Decode(t *testing.T) {
 		Authorization: []message.PermissionLevel{
 			{Actor: "mygame", Permission: "active"},
 		},
+		Except: "errstr",
+		Error:  2,
+		Return: []byte{0xde, 0xad, 0xbe, 0xef},
 	}
 
 	res := message.ActionTrace{}