diff --git a/partner-trugee.js b/partner-trugee.js
index 54ac7a1..b14e917 100644
--- a/partner-trugee.js
+++ b/partner-trugee.js
@@ -175,6 +175,7 @@ function createServer() {
 
     var httpServer = http.createServer(function(req, res) {
         //console.log('Got request from partner ("' + req.url + '")');
+        var sn;
 
         res.end('OK');
 
@@ -192,8 +193,14 @@ function createServer() {
             // refund
             response_code = '40';
         } else if (qs.code == 4) {
+
             response_code = '00';
-            message = 'SN=' + qs.sn + ';' + message;
+            sn = qs.sn;
+            if (sn && typeof sn === 'string') {
+                sn = sn.toUpperCase().replace(/[^A-Z0-9\/]/g, '-').replace(/-+/g, '-').replace(/-+\//g, '/').replace(/^-+/, '').replace(/-+$/, '-');
+            }
+
+            message = 'SN=' + qs.sn + '; ' + message;
         }
 
         if (response_code == '40') {