diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_5/Regress/regress-299641.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_5/Regress/regress-299641.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,24 @@
+/* -*- 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 = 299641;
+var summary = '12.6.4 - LHS for (LHS in expression) execution';
+var actual = '';
+var expect = 0;
+
+printBugNumber(BUGNUMBER);
+printStatus (summary);
+
+function f() {
+  var i = 0;
+  var a = [{x: 42}];
+  for (a[i++].x in [])
+    return(a[i-1].x);
+  return(i);
+}
+actual = f();
+ 
+reportCompare(expect, actual, summary);