diff --git a/client/tlv_decoders.go b/client/tlv_decoders.go
index 200e5370f..9d74ea450 100644
--- a/client/tlv_decoders.go
+++ b/client/tlv_decoders.go
@@ -109,7 +109,7 @@ func (c *QQClient) decodeT119(data, ek []byte) {
 
 	s.PsKeyMap = psKeyMap
 	s.Pt4TokenMap = pt4TokenMap
-	if len(c.PasswordMd5[:]) > 0 {
+	if len(c.sig.EncryptedA1) > 51+16 {
 		data, cl := binary.OpenWriterF(func(w *binary.Writer) {
 			w.Write(c.PasswordMd5[:])
 			w.WriteUInt32(0) // []byte{0x00, 0x00, 0x00, 0x00}...