diff --git a/CHANGELOG b/CHANGELOG
index 77bb59d..40bda7d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,5 @@
+* Ensure `toString` and `valueOf` properties are copied to a subclass only when necessary in IE6. [@382 state:resolved] (Samuel Lebeau)
+
 * Make sure `getAttribute` is used without flag when accessing the "type" attribute of an iframe (IE throws error otherwise). [#118 state:resolved] (Zekid, kangax)
 
 * String#gsub should escape RegExp metacharacters when the first argument is a string. [#469 state:resolved] (michael, kangax)
diff --git a/src/lang/class.js b/src/lang/class.js
index 0e3bd4a..2c335c9 100644
--- a/src/lang/class.js
+++ b/src/lang/class.js
@@ -83,7 +83,16 @@ var Class = (function() {
     
     if (!Object.keys({ toString: true }).length)
       properties.push("toString", "valueOf");
-    
+      
+    // IE6 doesn't enumerate toString and valueOf properties,        
+    // Force copy if they're not coming from Object.prototype.      
+    if (!Object.keys({ toString: true }).length) {
+      if (source.toString != Object.prototype.toString)
+        properties.push("toString");
+      if (source.valueOf != Object.prototype.valueOf)
+        properties.push("valueOf");
+    }
+                                                                 
     for (var i = 0, length = properties.length; i < length; i++) {
       var property = properties[i], value = source[property];
       if (ancestor && Object.isFunction(value) &&
diff --git a/test/unit/class_test.js b/test/unit/class_test.js
index 98e8e88..8c5e9c3 100644
--- a/test/unit/class_test.js
+++ b/test/unit/class_test.js
@@ -112,6 +112,10 @@ new Test.Unit.Runner({
       toString: function() { return "toString" },
       valueOf: function() { return "valueOf" }
     });
+    
+    var Bar = Class.create(Foo, {
+      valueOf: function() { return "myValueOf" }
+    });
 
     var Parent = Class.create({
       m1: function(){ return 'm1' },
@@ -126,5 +130,7 @@ new Test.Unit.Runner({
 
     this.assertEqual("toString", new Foo().toString());
     this.assertEqual("valueOf", new Foo().valueOf());
+    this.assertEqual("toString", new Bar().toString());
+    this.assertEqual("myValueOf", new Bar().valueOf());
   }
 });
\ No newline at end of file