diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_5/String/match-forward-lookahead.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_5/String/match-forward-lookahead.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,27 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ */
+
+var BUGNUMBER = 501739;
+var summary =
+  "String.prototype.match behavior with zero-length matches involving " +
+  "forward lookahead";
+
+print(BUGNUMBER + ": " + summary);
+
+/**************
+ * BEGIN TEST *
+ **************/
+
+var r = /(?=x)/g;
+
+var res = "aaaaaaaaaxaaaaaaaaax".match(r);
+assertEq(res.length, 2);
+
+/******************************************************************************/
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
+
+print("Tests complete");