diff -r 000000000000 -r 6474c204b198 js/src/tests/Intl/NumberFormat/StringBuffer.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/Intl/NumberFormat/StringBuffer.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,17 @@
+// |reftest| skip-if(!this.hasOwnProperty("Intl"))
+/* 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/. */
+
+// The implementation of the format function uses the C++ StringBuffer class,
+// which changes its storage model at 32 characters, and uses it in a way which
+// also means that there's no room for null-termination at this limit.
+// This test makes sure that none of this affects the output.
+
+var format = new Intl.NumberFormat("it-IT", {minimumFractionDigits: 1});
+
+assertEq(format.format(1123123123123123123123.1), "1.123.123.123.123.120.000.000,0");
+assertEq(format.format(12123123123123123123123.1), "12.123.123.123.123.100.000.000,0");
+assertEq(format.format(123123123123123123123123.1), "123.123.123.123.123.000.000.000,0");
+
+reportCompare(0, 0, "ok");