diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/bug821850.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/bug821850.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,9 @@
+load(libdir + "asserts.js");
+
+m={}
+Object.defineProperty(m, 'p', {value: 3});
+assertThrowsInstanceOf(function() {"use strict"; delete m.p;}, TypeError);
+
+x = new Proxy(m, {})
+assertEq(x.p, 3);
+assertThrowsInstanceOf(function fun() {"use strict"; return delete x.p; }, TypeError);