diff --git a/pkg/codec/json.go b/pkg/codec/json.go
index e0313f9c37c523dde65b592ee5d7967d8c908b54..7c8b9720172738fd7e05aa577123219ac0a12133 100644
--- a/pkg/codec/json.go
+++ b/pkg/codec/json.go
@@ -81,7 +81,7 @@ func (m *Message) UnmarshalJSON(xs []byte) error {
 			}
 			buf := bytes.NewBuffer(m.Params)
 			buf.Reset()
-			_, err := buf.Write(val)
+			_, err = buf.Write(val)
 			if err != nil {
 				return err
 			}
@@ -93,7 +93,7 @@ func (m *Message) UnmarshalJSON(xs []byte) error {
 			}
 			buf := bytes.NewBuffer(m.Result)
 			buf.Reset()
-			_, err := buf.Write(val)
+			_, err = buf.Write(val)
 			if err != nil {
 				return err
 			}