diff --git a/encoding/proto/proto.go b/encoding/proto/proto.go
index 0ecf4be0ecb0..3009b35afe7d 100644
--- a/encoding/proto/proto.go
+++ b/encoding/proto/proto.go
@@ -40,7 +40,7 @@ type codec struct{}
 func (codec) Marshal(v interface{}) ([]byte, error) {
 	vv, ok := v.(proto.Message)
 	if !ok {
-		return nil, fmt.Errorf("failed to marshal, message is %T, want proto", v)
+		return nil, fmt.Errorf("failed to marshal, message is %T, want proto.Message", v)
 	}
 	return proto.Marshal(vv)
 }
@@ -48,7 +48,7 @@ func (codec) Marshal(v interface{}) ([]byte, error) {
 func (codec) Unmarshal(data []byte, v interface{}) error {
 	vv, ok := v.(proto.Message)
 	if !ok {
-		return fmt.Errorf("failed to marshal, message is %T, want proto", v)
+		return fmt.Errorf("failed to unmarshal, message is %T, want proto.Message", v)
 	}
 	return proto.Unmarshal(data, vv)
 }