diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testSettingWatchPointOnReadOnlyProp.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testSettingWatchPointOnReadOnlyProp.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,7 @@
+for (var i = 0; i < 5; ++i) {
+    var o = {}
+    Object.defineProperty(o, 'x', { value:"cow", writable:false });
+    var r = o.watch('x', function() {});
+    assertEq(r, undefined);
+    o.x = 4;
+}