diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/debug/Object-defineProperty-10.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/debug/Object-defineProperty-10.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,10 @@
+// defineProperty can make a non-configurable writable property non-writable
+
+load(libdir + "asserts.js");
+var g = newGlobal();
+var dbg = new Debugger;
+var gw = dbg.addDebuggee(g);
+gw.defineProperty("p", {writable: true, value: 1});
+gw.defineProperty("p", {writable: false});
+g.p = 4;
+assertEq(g.p, 1);