diff --git a/gentong.js b/gentong.js
index ed392bf..f95c7d0 100644
--- a/gentong.js
+++ b/gentong.js
@@ -211,6 +211,8 @@ function createServer() {
                 sn = paddingSN(sn, config);
             }
 
+            sn = sn.trim();
+
         } else if (qs.topup_status == 'R') {
 
             response_code = '40';