diff --git a/protocol/shadowsocks/shadowaead_2022/protocol.go b/protocol/shadowsocks/shadowaead_2022/protocol.go
index 999cef9..19b418c 100644
--- a/protocol/shadowsocks/shadowaead_2022/protocol.go
+++ b/protocol/shadowsocks/shadowaead_2022/protocol.go
@@ -444,7 +444,7 @@ func (c *clientPacketConn) WritePacket(buffer *buf.Buffer, destination M.Socksad
 		if pskLen > 1 {
 			panic("unsupported chacha extended header")
 		}
-		dataIndex = buffer.Len()
+		dataIndex = PacketNonceSize
 	} else {
 		dataIndex = aes.BlockSize
 	}
@@ -649,7 +649,7 @@ func (c *clientPacketConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
 		if pskLen > 1 {
 			panic("unsupported chacha extended header")
 		}
-		dataIndex = buffer.Len()
+		dataIndex = PacketNonceSize
 	} else {
 		dataIndex = aes.BlockSize
 	}
diff --git a/protocol/shadowsocks/shadowaead_2022/service.go b/protocol/shadowsocks/shadowaead_2022/service.go
index dd2d282..6fdf2c2 100644
--- a/protocol/shadowsocks/shadowaead_2022/service.go
+++ b/protocol/shadowsocks/shadowaead_2022/service.go
@@ -8,6 +8,7 @@ import (
 	"io"
 	"math"
 	"net"
+	"os"
 	"runtime"
 	"sync"
 	"sync/atomic"
@@ -69,16 +70,20 @@ func NewService(method string, psk []byte, password string, secureRNG io.Reader,
 	case "2022-blake3-chacha20-poly1305":
 		s.keySaltLength = 32
 		s.constructor = newChacha20Poly1305
+	default:
+		return nil, os.ErrInvalid
 	}
 
-	if len(psk) < s.keySaltLength {
-		return nil, shadowsocks.ErrBadKey
-	} else if len(psk) > s.keySaltLength {
-		psk = Key(psk, s.keySaltLength)
-	} else if password == "" {
-		return nil, ErrMissingPasswordPSK
-	} else {
-		psk = Key([]byte(password), s.keySaltLength)
+	if len(psk) != s.keySaltLength {
+		if len(psk) < s.keySaltLength {
+			return nil, shadowsocks.ErrBadKey
+		} else if len(psk) > s.keySaltLength {
+			psk = Key(psk, s.keySaltLength)
+		} else if password == "" {
+			return nil, ErrMissingPasswordPSK
+		} else {
+			psk = Key([]byte(password), s.keySaltLength)
+		}
 	}
 
 	switch method {
@@ -395,7 +400,7 @@ func (w *serverPacketWriter) WritePacket(buffer *buf.Buffer, destination M.Socks
 	var dataIndex int
 	if w.udpCipher != nil {
 		common.Must1(header.ReadFullFrom(w.secureRNG, PacketNonceSize))
-		dataIndex = buffer.Len()
+		dataIndex = PacketNonceSize
 	} else {
 		dataIndex = aes.BlockSize
 	}