diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8/genexps/regress-384991.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8/genexps/regress-384991.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,59 @@
+/* -*- 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 = 384991;
+var summary = ' w(yield) should not cause "yield expression must be parenthesized" syntax error';
+var actual = '';
+var expect = '';
+
+
+//-----------------------------------------------------------------------------
+test();
+//-----------------------------------------------------------------------------
+
+function test()
+{
+  enterFunc ('test');
+  printBugNumber(BUGNUMBER);
+  printStatus (summary);
+
+  expect = 'No Error';
+
+  try
+  {
+    actual = 'No Error';
+    (function() { w((yield)); });
+  }
+  catch(ex)
+  {
+    actual = ex + '';
+  }
+  reportCompare(expect, actual, summary + ': 1');
+
+  try
+  {
+    actual = 'No Error';
+    (function() { w(1 ? yield : 0); });
+  }
+  catch(ex)
+  {
+    actual = ex + '';
+  }
+  reportCompare(expect, actual, summary + ': 2');
+
+  try
+  {
+    actual = 'No Error';
+    (function () { f(x = yield); const x; });
+  }
+  catch(ex)
+  {
+    actual = ex + '';
+  }
+  reportCompare(expect, actual, summary + ': 3');
+
+  exitFunc ('test');
+}