diff --git a/src/Entrance.php b/src/Entrance.php
index af57cba..a8c69ef 100644
--- a/src/Entrance.php
+++ b/src/Entrance.php
@@ -80,6 +80,6 @@ public function chatRoom() {
      * @return bool
      */
     public function isLegalChecksum($body, $curTime, $checksumPost) {
-        return sha1($this->appSecrt . md5($body), $curTime) === $checksumPost;
+        return sha1($this->appSecrt . md5($body) . $curTime) === $checksumPost;
     }
 }