diff --git a/lib/serializer.js b/lib/serializer.js
index <HASH>..<HASH> 100644
--- a/lib/serializer.js
+++ b/lib/serializer.js
@@ -257,7 +257,7 @@ Swiz.prototype._serializeXml = function(obj, key) {
 
     for (i = 0; i < keys.length; i++) {
       if (obj.hasOwnProperty(keys[i])) {
-        if (this.options.stripNulls && (obj[keys[i]] === null || obj[keys[i]] === null)) {
+        if (this.options.stripNulls && (obj[keys[i]] === null || obj[keys[i]] === undefined)) {
         } else {
           result += this._serializeXml(obj[keys[i]], this.xmlEscapeString(keys[i]));
         }
oops, this should be undefined.