diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_5/Regress/regress-418504.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_5/Regress/regress-418504.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,53 @@
+/* -*- 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 = 418504;
+var summary = 'Untagged boolean stored in a jsval in JS_ConvertValue';
+var actual = '';
+var expect = '';
+
+
+//-----------------------------------------------------------------------------
+test();
+//-----------------------------------------------------------------------------
+
+function test()
+{
+  enterFunc ('test');
+  printBugNumber(BUGNUMBER);
+  printStatus (summary);
+ 
+  expect = false;
+  actual = RegExp.multiline;
+  reportCompare(expect, actual, 'RegExp.multiline');
+
+  expect = true;
+  RegExp.multiline = 17;
+  actual = RegExp.multiline;
+  reportCompare(expect, actual, 'RegExp.multiline = 17');
+
+  expect = true;
+  RegExp.multiline = 17;
+  actual = RegExp.multiline;
+  reportCompare(expect, actual, 'RegExp.multiline = 17');
+
+  expect = true;
+  RegExp.multiline = 17;
+  actual = RegExp.multiline;
+  reportCompare(expect, actual, 'RegExp.multiline = 17');
+
+  expect = true;
+  RegExp.multiline = true;
+  actual = RegExp.multiline;
+  reportCompare(expect, actual, 'RegExp.multiline = true');
+
+  expect = true;
+  RegExp.multiline = 17;
+  actual = RegExp.multiline;
+  reportCompare(expect, actual, 'RegExp.multiline = 17');
+
+  exitFunc ('test');
+}