diff --git a/src/lib/js2xml.ts b/src/lib/js2xml.ts
index 0ee38ce..4eb3ff9 100644
--- a/src/lib/js2xml.ts
+++ b/src/lib/js2xml.ts
@@ -109,7 +109,7 @@ export class Js2xml {
    * Convert a javascript object to a valid xmlrpc value (as xml element).
    */
   convert(doc:Document, input:any):Node {
-    const type = input!==null ?
+    const type = input!==null && (typeof input!=="undefined") ?
         Object.prototype.toString.call(input).slice(8, -1).toLowerCase() : 'nil'
     let method = this.js2xmlMethod['string']
     try {