diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8_1/regress/regress-495907.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8_1/regress/regress-495907.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,36 @@
+/* -*- 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 = 495907;
+var summary = 'Read upvar from trace-entry frame when created with top-level let';
+var actual = ''
+var expect = '00112233';
+//-----------------------------------------------------------------------------
+
+// The test code needs to run at top level in order to expose the bug.
+start_test();
+
+var o = [];
+for (let a = 0; a < 4; ++a) {
+    (function () {for (var b = 0; b < 2; ++b) {o.push(a);}}());
+}
+actual = o.join("");
+
+finish_test();
+//-----------------------------------------------------------------------------
+
+function start_test() {
+  enterFunc ('test');
+  printBugNumber(BUGNUMBER);
+  printStatus (summary);
+  jit(true);
+}
+
+function finish_test() {
+  jit(false);
+  reportCompare(expect, actual, summary);
+  exitFunc ('test');
+}