diff --git a/xmlout.js b/xmlout.js
index 3955ca4..1ad27dc 100644
--- a/xmlout.js
+++ b/xmlout.js
@@ -189,9 +189,10 @@ function prefixMessageWithSN(data) {
     }
 
     if (sn) {
-        sn = sn.replace(/ /g, '-');
-        sn = sn.replace(/[\()]/g, '-');
-        sn = sn.replace(/-+/g, '-')
+        //sn = sn.replace(/ /g, '-');
+        //sn = sn.replace(/[\()]/g, '-');
+        sn = sn.replace(/[^A-Z0-9\/]/g, '-');
+        sn = sn.replace(/-+/g, '-');
         sn = sn.replace(/^-+/, '');
         sn = sn.replace(/-+$/, '');
         sn = sn.replace(/;\s*SN=.+?;/, '; ');