diff --git a/file.go b/file.go
index 45dedd7..57d8752 100644
--- a/file.go
+++ b/file.go
@@ -8,13 +8,15 @@ import (
 	"regexp"
 
 	"dario.cat/mergo"
-	"go.unistack.org/micro/v3/codec"
 	"go.unistack.org/micro/v3/config"
 	rutil "go.unistack.org/micro/v3/util/reflect"
 	"golang.org/x/text/transform"
 )
 
-var DefaultStructTag = "file"
+var (
+	DefaultStructTag       = "file"
+	MaxFileSize      int64 = 1 * 1024 * 1024
+)
 
 type fileConfig struct {
 	opts        config.Options
@@ -129,7 +131,7 @@ func (c *fileConfig) Load(ctx context.Context, opts ...config.LoadOption) error
 		r = fp
 	}
 
-	buf, err := io.ReadAll(io.LimitReader(r, int64(codec.DefaultMaxMsgSize)))
+	buf, err := io.ReadAll(io.LimitReader(r, MaxFileSize))
 	if err != nil {
 		if !c.opts.AllowFail {
 			return err
diff --git a/file_test.go b/file_test.go
index 2cb7c61..376471d 100644
--- a/file_test.go
+++ b/file_test.go
@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"io"
 	"os"
 	"testing"
 
@@ -22,22 +21,10 @@ func (*jsoncodec) Unmarshal(buf []byte, v interface{}, opts ...codec.Option) err
 	return json.Unmarshal(buf, v)
 }
 
-func (*jsoncodec) ReadBody(r io.Reader, v interface{}) error {
-	return nil
-}
-
-func (*jsoncodec) ReadHeader(r io.Reader, m *codec.Message, t codec.MessageType) error {
-	return nil
-}
-
 func (*jsoncodec) String() string {
 	return "json"
 }
 
-func (*jsoncodec) Write(w io.Writer, m *codec.Message, v interface{}) error {
-	return nil
-}
-
 func TestLoadReplace(t *testing.T) {
 	type Config struct {
 		Key  string
diff --git a/watcher.go b/watcher.go
index 8088636..6bc3653 100644
--- a/watcher.go
+++ b/watcher.go
@@ -7,7 +7,6 @@ import (
 	"os"
 	"reflect"
 
-	"go.unistack.org/micro/v3/codec"
 	"go.unistack.org/micro/v3/config"
 	"go.unistack.org/micro/v3/util/jitter"
 	rutil "go.unistack.org/micro/v3/util/reflect"
@@ -44,7 +43,7 @@ func (w *fileWatcher) run() {
 					return
 				}
 				var buf []byte
-				buf, err = ioutil.ReadAll(io.LimitReader(fp, int64(codec.DefaultMaxMsgSize)))
+				buf, err = ioutil.ReadAll(io.LimitReader(fp, MaxFileSize))
 				if err == nil {
 					err = w.opts.Codec.Unmarshal(buf, dst)
 				}