diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/jaeger/propertyOptimize-4.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/jaeger/propertyOptimize-4.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,17 @@
+// Make sure new script properties can be invalidated on specialized prototype
+// types while they are still being constructed.
+
+function Foo(a, b, c) {
+  this.x = a + b;
+  this.y = c;
+}
+
+updated = false;
+var o = {valueOf: function() {
+    Object.defineProperty(Object.prototype, 'y', {set:function() { updated = true; }})
+  }};
+
+function Bar() {}
+Bar.prototype = new Foo(o, 1, 2);
+assertEq(updated, true);
+assertEq(Bar.prototype.y, undefined);