diff --git a/cmd/gocq/login.go b/cmd/gocq/login.go
index 240fcf90c..d830e99fd 100644
--- a/cmd/gocq/login.go
+++ b/cmd/gocq/login.go
@@ -315,8 +315,11 @@ func signSubmit(uin string, cmd string, callbackID int64, buffer []byte, t strin
 		signServer += "/"
 	}
 	buffStr := hex.EncodeToString(buffer)
-	log.Infof("submit %v: uin=%v, cmd=%v, callbackID=%v, buffer-end=%v", t, uin, cmd, callbackID,
-		buffStr[len(buffStr)-10:])
+	buffEnd := buffStr
+	if len(buffEnd) > 10 {
+		buffEnd = buffEnd[len(buffEnd)-10:]
+	}
+	log.Infof("submit %v: uin=%v, cmd=%v, callbackID=%v, buffer-end=%v", t, uin, cmd, callbackID, buffEnd)
 	_, err := download.Request{
 		Method: http.MethodGet,
 		URL: signServer + "submit" + fmt.Sprintf("?uin=%v&cmd=%v&callback_id=%v&buffer=%v",