diff --git a/wchat/wx/V3/WxV3PaymentTait.php b/wchat/wx/V3/WxV3PaymentTait.php
index c64d5d5..eb1833a 100644
--- a/wchat/wx/V3/WxV3PaymentTait.php
+++ b/wchat/wx/V3/WxV3PaymentTait.php
@@ -41,7 +41,7 @@ trait WxV3PaymentTait
     {
         $rand = md5(random_bytes(32));
         $time = time();
-        $message = sprintf("%s\n%s\n%d\n%s\n\n", $http_method, $canonical_url, $time, $rand);
+        $message = sprintf("%s\n%s\n%d\n%s\n[]\n", $http_method, $canonical_url, $time, $rand);
 
         $sign = $this->openssl_signature($message);