diff --git a/config/config.go b/config/config.go
index 3d5c460d6..382123c24 100644
--- a/config/config.go
+++ b/config/config.go
@@ -3,11 +3,11 @@ package config
 import (
 	"context"
 	"errors"
-	"github.com/go-kratos/kratos/v2/encoding"
 	"reflect"
 	"sync"
 	"time"
 
+	"github.com/go-kratos/kratos/v2/encoding"
 	// init encoding
 	_ "github.com/go-kratos/kratos/v2/encoding/json"
 	_ "github.com/go-kratos/kratos/v2/encoding/proto"
diff --git a/config/config_test.go b/config/config_test.go
index 9a166b00e..090c3cd3f 100644
--- a/config/config_test.go
+++ b/config/config_test.go
@@ -3,6 +3,9 @@ package config
 import (
 	"errors"
 	"testing"
+
+	"github.com/go-kratos/kratos/v2/encoding"
+	_ "github.com/go-kratos/kratos/v2/encoding/json"
 )
 
 const (
@@ -128,9 +131,10 @@ func TestConfig(t *testing.T) {
 
 	jSource := newTestJSONSource(_testJSON)
 	opts := options{
-		sources:  []Source{jSource},
-		decoder:  defaultDecoder,
-		resolver: defaultResolver,
+		sources:    []Source{jSource},
+		decoder:    defaultDecoder,
+		resolver:   defaultResolver,
+		mergeCodec: encoding.GetCodec("json"),
 	}
 	cf := &config{}
 	cf.opts = opts
diff --git a/config/reader_test.go b/config/reader_test.go
index 11b2d990e..d46890996 100644
--- a/config/reader_test.go
+++ b/config/reader_test.go
@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"github.com/go-kratos/kratos/v2/encoding"
+	_ "github.com/go-kratos/kratos/v2/encoding/json"
 )
 
 func TestReader_Merge(t *testing.T) {
@@ -183,7 +184,8 @@ func TestReader_Source(t *testing.T) {
 			}
 			return fmt.Errorf("unsupported key: %s format: %s", kv.Key, kv.Format)
 		},
-		resolver: defaultResolver,
+		resolver:   defaultResolver,
+		mergeCodec: encoding.GetCodec("json"),
 	}
 	r := newReader(opts)
 	err = r.Merge(&KeyValue{