diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_3/Regress/regress-420087.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_3/Regress/regress-420087.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,31 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 420087;
+var summary = 'Do not assert:  PCVCAP_MAKE(sprop->shape, 0, 0) == entry->vcap';
+var actual = 'No Crash';
+var expect = 'No Crash';
+
+
+//-----------------------------------------------------------------------------
+test();
+//-----------------------------------------------------------------------------
+
+function test()
+{
+  enterFunc ('test');
+  printBugNumber(BUGNUMBER);
+  printStatus (summary);
+
+  var dict;
+
+  for (var i = 0; i < 2; i++)
+    dict = {p: 1, q: 1, p:1};
+
+  reportCompare(expect, actual, summary);
+
+  exitFunc ('test');
+}