diff --git a/infra/conf/v5cfg/outbound.go b/infra/conf/v5cfg/outbound.go
index 38983fdfea..ac864683b0 100644
--- a/infra/conf/v5cfg/outbound.go
+++ b/infra/conf/v5cfg/outbound.go
@@ -2,8 +2,6 @@ package v5cfg
 
 import (
 	"context"
-	"strings"
-
 	"github.com/golang/protobuf/proto"
 
 	core "github.com/v2fly/v2ray-core/v5"
@@ -42,15 +40,18 @@ func (c OutboundConfig) BuildV5(ctx context.Context) (proto.Message, error) {
 	if c.MuxSettings != nil {
 		senderSettings.MultiplexSettings = c.MuxSettings.Build()
 	}
-	
+
 	senderSettings.DomainStrategy = proxyman.SenderConfig_AS_IS
-	switch strings.ToLower(c.DomainStrategy) {
-	case "useip", "use_ip", "use-ip":
+	switch c.DomainStrategy {
+	case "UseIP":
 		senderSettings.DomainStrategy = proxyman.SenderConfig_USE_IP
-	case "useip4", "useipv4", "use_ip4", "use_ipv4", "use_ip_v4", "use-ip4", "use-ipv4", "use-ip-v4":
+	case "UseIP4":
 		senderSettings.DomainStrategy = proxyman.SenderConfig_USE_IP4
-	case "useip6", "useipv6", "use_ip6", "use_ipv6", "use_ip_v6", "use-ip6", "use-ipv6", "use-ip-v6":
+	case "UseIP6":
 		senderSettings.DomainStrategy = proxyman.SenderConfig_USE_IP6
+	case "AsIs", "":
+	default:
+		return nil, newError("unknown domain strategy: ", c.DomainStrategy)
 	}
 
 	if c.Settings == nil {