diff --git a/src/base.js b/src/base.js
index 6120c41..eae7f18 100644
--- a/src/base.js
+++ b/src/base.js
@@ -159,7 +159,7 @@ Object.extend(Object, {
 
 Object.extend(Function.prototype, {
   argumentNames: function() {
-    var names = this.toString().match(/^[\s\(]*function[^(]*\((.*?)\)/)[1].split(/\s*,\s*/);
+    var names = this.toString().match(/^[\s\(]*function[^(]*\(\s*(.*?)\s*\)/)[1].split(/\s*,\s*/);
     return names.length == 1 && !names[0] ? [] : names;
   },
   
diff --git a/test/unit/base_test.js b/test/unit/base_test.js
index 8b6a466..73e268f 100644
--- a/test/unit/base_test.js
+++ b/test/unit/base_test.js
@@ -3,6 +3,7 @@ new Test.Unit.Runner({
     this.assertEnumEqual([], (function() {}).argumentNames());
     this.assertEnumEqual(["one"], (function(one) {}).argumentNames());
     this.assertEnumEqual(["one", "two", "three"], (function(one, two, three) {}).argumentNames());
+    this.assertEnumEqual(["one", "two", "three"], (function(  one  , two  , three   ) {}).argumentNames());
     this.assertEqual("$super", (function($super) {}).argumentNames().first());
     
     function named1() {};