diff --git a/source/Ox/js/Encoding.js b/source/Ox/js/Encoding.js
index 27e702a3..940b228f 100644
--- a/source/Ox/js/Encoding.js
+++ b/source/Ox/js/Encoding.js
@@ -243,7 +243,8 @@ Ox.encodeHTML <f> HTML-encodes a string
     '&#x00E4;b&#x00E7;d&#x00EA;'
 @*/
 Ox.encodeHTML = function(string) {
-    return Ox.map(string.toString(), function(char) {
+    string = Ox.isUndefined(string) ? '' : string.toString();
+    return Ox.map(string, function(char) {
         var code = char.charCodeAt(0);
         return code < 128
             ? (char in Ox.HTML_ENTITIES ? Ox.HTML_ENTITIES[char] : char)