diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/pic/watch3b.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/pic/watch3b.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,20 @@
+// assignment to watched global properties must not be traced
+var hits = 0;
+function counter(id, oldval, newval) {
+    hits++;
+    return newval;
+}
+
+var x = 0;
+var y = 0;
+function f() {
+    var a = [{}, this];
+    for (var i = 0; i < 14; i++) {
+        print(shapeOf(this));
+        Object.prototype.watch.call(a[+(i > 8)], "y", counter);
+        y++;
+    }
+}
+f();
+assertEq(hits, 5);
+