diff --git a/common/json/badjson/merge.go b/common/json/badjson/merge.go
index b6534d8..61b5f4c 100644
--- a/common/json/badjson/merge.go
+++ b/common/json/badjson/merge.go
@@ -1,6 +1,7 @@
 package badjson
 
 import (
+	"os"
 	"reflect"
 
 	"github.com/sagernet/sing/common"
@@ -42,6 +43,9 @@ func Merge[T any](source T, destination T) (T, error) {
 }
 
 func MergeFromSource[T any](rawSource json.RawMessage, destination T) (T, error) {
+	if rawSource == nil {
+		return destination, nil
+	}
 	rawDestination, err := json.Marshal(destination)
 	if err != nil {
 		return common.DefaultValue[T](), E.Cause(err, "marshal destination")
@@ -50,6 +54,9 @@ func MergeFromSource[T any](rawSource json.RawMessage, destination T) (T, error)
 }
 
 func MergeFromDestination[T any](source T, rawDestination json.RawMessage) (T, error) {
+	if rawDestination == nil {
+		return source, nil
+	}
 	rawSource, err := json.Marshal(source)
 	if err != nil {
 		return common.DefaultValue[T](), E.Cause(err, "marshal source")
@@ -71,6 +78,13 @@ func MergeFrom[T any](rawSource json.RawMessage, rawDestination json.RawMessage)
 }
 
 func MergeJSON(rawSource json.RawMessage, rawDestination json.RawMessage) (json.RawMessage, error) {
+	if rawSource == nil && rawDestination == nil {
+		return nil, os.ErrInvalid
+	} else if rawSource == nil {
+		return rawDestination, nil
+	} else if rawDestination == nil {
+		return rawSource, nil
+	}
 	source, err := Decode(rawSource)
 	if err != nil {
 		return nil, E.Cause(err, "decode source")