diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8_5/extensions/regress-604781-1.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8_5/extensions/regress-604781-1.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,24 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/licenses/publicdomain/
+
+var watcherCount, setterCount;
+function watcher(id, oldval, newval) { watcherCount++; return newval; }
+function setter(newval) { setterCount++; }
+
+var p = { set x(v) { setter(v); } };
+p.watch('x', watcher);
+
+watcherCount = setterCount = 0;
+p.x = 2;
+assertEq(setterCount, 1);
+assertEq(watcherCount, 1);
+
+var o = Object.defineProperty({}, 'x', { set:setter, enumerable:true, configurable:true });
+o.watch('x', watcher);
+
+watcherCount = setterCount = 0;
+o.x = 2;
+assertEq(setterCount, 1);
+assertEq(watcherCount, 1);
+
+reportCompare(0, 0, 'ok');