diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_5/misc/explicit-undefined-optional-argument.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_5/misc/explicit-undefined-optional-argument.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,34 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/licenses/publicdomain/
+
+var BUGNUMBER = 373118;
+var summary =
+  'Properly handle explicitly-undefined optional arguments to a bunch of ' +
+  'functions';
+
+print(BUGNUMBER + ": " + summary);
+
+//-----------------------------------------------------------------------------
+
+var a;
+
+a = "abc".slice(0, undefined);
+assertEq(a, "abc");
+
+a = "abc".substr(0, undefined);
+assertEq(a, "abc");
+
+a = "abc".substring(0, undefined);
+assertEq(a, "abc");
+
+a = [1, 2, 3].slice(0, undefined);
+assertEq(a.join(), '1,2,3');
+
+a = [1, 2, 3].sort(undefined);
+assertEq(a.join(), '1,2,3');
+
+assertEq((20).toString(undefined), '20');
+
+//-----------------------------------------------------------------------------
+
+reportCompare(true, true);