diff --git a/option/types.go b/option/types.go
index d97614da..f2df2ca2 100644
--- a/option/types.go
+++ b/option/types.go
@@ -2,7 +2,6 @@ package option
 
 import (
 	"net/netip"
-	"strings"
 	"time"
 
 	"github.com/sagernet/sing-box/common/json"
@@ -50,10 +49,13 @@ func (a *ListenAddress) Build() netip.Addr {
 	return (netip.Addr)(*a)
 }
 
-type NetworkList string
+type NetworkList []string
 
-func (v *NetworkList) UnmarshalJSON(content []byte) (err error) {
-	var networkList []string
+func (v *NetworkList) UnmarshalJSON(content []byte) error {
+	var (
+		networkList []string
+		err         error
+	)
 	if len(content) > 0 && content[0] != '[' {
 		networkList = make([]string, 1)
 		err = json.Unmarshal(content, &networkList[0])
@@ -61,25 +63,25 @@ func (v *NetworkList) UnmarshalJSON(content []byte) (err error) {
 		err = json.Unmarshal(content, &networkList)
 	}
 	if err != nil {
-		return
+		return err
 	}
 	for _, networkName := range networkList {
 		switch networkName {
 		case N.NetworkTCP, N.NetworkUDP:
 			break
 		default:
-			return E.New("unknown network: " + networkName)
+			return E.Extend(N.ErrUnknownNetwork, networkName)
 		}
 	}
-	*v = NetworkList(strings.Join(networkList, "\n"))
-	return
+	*v = networkList
+	return nil
 }
 
 func (v NetworkList) Build() []string {
-	if v == "" {
+	if len(v) == 0 {
 		return []string{N.NetworkTCP, N.NetworkUDP}
 	}
-	return strings.Split(string(v), "\n")
+	return v
 }
 
 type Listable[T comparable] []T
@@ -91,13 +93,14 @@ func (l Listable[T]) MarshalJSON() ([]byte, error) {
 	return json.Marshal([]T(l))
 }
 
-func (l *Listable[T]) UnmarshalJSON(content []byte) (err error) {
+func (l *Listable[T]) UnmarshalJSON(content []byte) error {
 	if len(content) > 0 && content[0] != '[' {
 		var element T
-		if err = json.Unmarshal(content, &element); err == nil {
+		err := json.Unmarshal(content, &element)
+		if err == nil {
 			*l = []T{element}
+			return nil
 		}
-		return
 	}
 	return json.Unmarshal(content, (*[]T)(l))
 }