diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/bug642894.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/bug642894.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,9 @@
+
+function foo() {
+  var x = {};
+  x.__proto__ = function() { return 0 }
+  return x;
+}
+var a = foo();
+var b = foo();
+assertEq(a.__proto__ === b.__proto__, false);