diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/for-of/next-arity.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/for-of/next-arity.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,22 @@
+// For-of passes one arg to "next".
+
+load(libdir + 'iteration.js')
+
+var log = '';
+
+function Iter() {
+    function next() {
+        log += 'n';
+        assertEq(arguments.length, 1)
+        assertEq(arguments[0], undefined)
+        return { get value() { throw 42; }, done: true }
+    }
+
+    this[std_iterator] = function () { return this; }
+    this.next = next;
+}
+
+for (var x of new Iter())
+    throw 'not reached';
+
+assertEq(log, 'n');