diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/collections/Array-of-length-setter-2.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/collections/Array-of-length-setter-2.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,13 @@
+// Array.of does a strict assignment to the new object's .length.
+// The assignment is strict even if the code we're calling from is not strict.
+
+load(libdir + "asserts.js");
+
+function Empty() {}
+Empty.of = Array.of;
+Object.defineProperty(Empty.prototype, "length", {get: () => 0});
+
+var nothing = new Empty;
+nothing.length = 2;  // no exception; this is not a strict mode assignment
+
+assertThrowsInstanceOf(() => Empty.of(), TypeError);