diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/mathRoundBig.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/mathRoundBig.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,10 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ */
+
+assertEq(Math.round(9007199254740991), 9007199254740991);
+assertEq(Math.round(-19007199254740990), -19007199254740990);
+
+assertEq(Math.round("9007199254740991"), 9007199254740991);
+assertEq(Math.round("-19007199254740990"), -19007199254740990);