diff --git a/mustache.js b/mustache.js
index 6d7c8a1..e356521 100644
--- a/mustache.js
+++ b/mustache.js
@@ -194,7 +194,7 @@ var Mustache = function() {
       Does away with nasty characters
     */
     escape: function(s) {
-      return s.toString().replace(/[&"<>\\]/g, function(s) {
+      return (s ? s.toString() : "").replace(/[&"<>\\]/g, function(s) {
         switch(s) {
           case "&": return "&amp;";
           case "\\": return "\\\\";;