diff -r 000000000000 -r 6474c204b198 js/src/jsapi-tests/testPropCache.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jsapi-tests/testPropCache.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ */
+/* 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/. */
+
+#include "jsapi-tests/tests.h"
+
+static int g_counter;
+
+static bool
+CounterAdd(JSContext *cx, JS::HandleObject obj, JS::HandleId id, JS::MutableHandleValue vp)
+{
+    g_counter++;
+    return true;
+}
+
+static const JSClass CounterClass = {
+    "Counter",  /* name */
+    0,  /* flags */
+    CounterAdd, JS_DeletePropertyStub, JS_PropertyStub, JS_StrictPropertyStub,
+    JS_EnumerateStub, JS_ResolveStub, JS_ConvertStub
+};
+
+BEGIN_TEST(testPropCache_bug505798)
+{
+    g_counter = 0;
+    EXEC("var x = {};");
+    CHECK(JS_DefineObject(cx, global, "y", &CounterClass, nullptr, JSPROP_ENUMERATE));
+    EXEC("var arr = [x, y];\n"
+         "for (var i = 0; i < arr.length; i++)\n"
+         "    arr[i].p = 1;\n");
+    CHECK_EQUAL(g_counter, 1);
+    return true;
+}
+END_TEST(testPropCache_bug505798)