diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_5/Array/regress-255555.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_5/Array/regress-255555.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,32 @@
+/* -*- 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 = 255555;
+var summary = 'Array.prototype.sort(comparefn) never passes undefined to comparefn';
+var actual = 'not undefined';
+var expect = 'not undefined';
+
+printBugNumber(BUGNUMBER);
+printStatus (summary);
+ 
+function comparefn(a,b)
+{
+  if (typeof a == 'undefined')
+  {
+    actual = 'undefined';
+    return 1;
+  }
+  if (typeof b == 'undefined')
+  {
+    actual = 'undefined';
+    return -1;
+  }
+  return a - b;
+}
+
+var arry = [ 1, 2, undefined ].sort(comparefn)
+
+  reportCompare(expect, actual, summary);