diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8_1/extensions/regress-520572.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8_1/extensions/regress-520572.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,41 @@
+/* -*- Mode: java; tab-width:8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ * Contributor: Blake Kaplan
+ */
+
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 520572;
+var summary = 'watch should innerize the object being watched';
+var actual = 0;
+var expect = 2;
+
+
+//-----------------------------------------------------------------------------
+test();
+//-----------------------------------------------------------------------------
+
+function test()
+{
+  enterFunc ('test');
+  printBugNumber(BUGNUMBER);
+  printStatus (summary);
+
+  if ("evalcx" in this) {
+      // shell
+      let s = evalcx("lazy");
+      s.n = 0;
+      evalcx('this.watch("x", function(){ n++; }); this.x = 4; x = 6', s);
+      actual = s.n;
+      reportCompare(expect, actual, summary);
+  } else {
+      // browser
+      this.watch('x', function(){ actual++; });
+      this.x = 4;
+      x = 6;
+      reportCompare(expect, actual, summary);
+  }
+
+  exitFunc ('test');
+}