diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/ion/bug784385.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/ion/bug784385.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,9 @@
+Object.defineProperty(Object.prototype, "a", {
+    set: function(a) { eval(""); return 123; }
+});
+var obj = {};
+var obj2 = {x: 1};
+for (var i = 0; i < 100; i++) {
+    var res = (obj.a = obj2);
+    res.x = 0xbeef;
+}