diff --git a/CHANGELOG b/CHANGELOG
index 67dc3c6..92f58bf 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,5 @@
+* Ensure Hash does not return keys from the prototype chain (e.g., constructor, valueOf, toString). (kangax)
+
 * Fix toString/valueOf sharing same method reference via closure in Class#addMethods. Use plain property assignment, since Object.extend fails to enumerate over toString/valueOf. (kangax)
 
 * Stop Form.Element.disable from stealing focus. (jddalton)
diff --git a/src/hash.js b/src/hash.js
index 125a96b..ed96637 100644
--- a/src/hash.js
+++ b/src/hash.js
@@ -28,7 +28,9 @@ var Hash = Class.create(Enumerable, (function() {
     },
 
     get: function(key) {
-      return this._object[key];
+      // simulating poorly supported hasOwnProperty
+      if (this._object[key] !== Object.prototype[key])
+        return this._object[key];
     },
 
     unset: function(key) {
diff --git a/test/unit/hash_test.js b/test/unit/hash_test.js
index f67ebca..cc3d083 100644
--- a/test/unit/hash_test.js
+++ b/test/unit/hash_test.js
@@ -14,6 +14,9 @@ new Test.Unit.Runner({
     this.assertEqual('A', h.get('a'));
     this.assertUndefined(h.a);
     this.assertUndefined($H({}).get('a'));
+
+    this.assertUndefined($H({}).get('toString'));
+    this.assertUndefined($H({}).get('constructor'));
   },
   
   testUnset: function() {