diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/proxy/testDirectProxyValidateProperty4.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/proxy/testDirectProxyValidateProperty4.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,24 @@
+load(libdir + "asserts.js");
+
+/*
+ * Throw a TypeError if both the current descriptor and the descriptor returned
+ * by the trap are data descriptors, the current descriptor is non-configurable
+ * and non-writable, and the descriptor returned by the trap is writable.
+ */
+var target = {};
+Object.defineProperty(target, 'foo', {
+    value: 'bar',
+    writable: false,
+    configurable: false
+});
+assertThrowsInstanceOf(function () { 
+    Object.getOwnPropertyDescriptor(new Proxy(target, {
+        getOwnPropertyDescriptor: function (target, name) {
+            return {
+                value: 'bar',
+                writable: true,
+                configurable: false
+            };
+        }
+    }), 'foo');
+}, TypeError);