diff --git a/CHANGELOG b/CHANGELOG
index 747b0f165..d96a52c8c 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,5 @@
+* Make Function#argumentNames use Function.prototype.toString. [Garrett Smith, jddalton, kangax]
+
 * Rename variable in Form.Element.Serializers.select. [jddalton]
 
 * Replace browser sniffing with capability detection in IE fork of String#unescapeHTML. [kangax]
diff --git a/src/base.js b/src/base.js
index 3b38887f5..73328d387 100644
--- a/src/base.js
+++ b/src/base.js
@@ -158,9 +158,10 @@ Object.extend(Object, {
 });
 
 Object.extend(Function.prototype, {
-  argumentNames: function() {
-    var names = this.toString().match(/^[\s\(]*function[^(]*\(([^\)]*)\)/)[1]
-      .replace(/\s+/g, '').split(',');
+  argumentNames: function() {  
+    var names = Function.prototype.toString.call(this)
+     .match(/^[\s\(]*function[^(]*\(([^\)]*)\)/)[1]
+     .replace(/\s+/g, '').split(',');
     return names.length == 1 && !names[0] ? [] : names;
   },