diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testIncDecReadOnly.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testIncDecReadOnly.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,22 @@
+var r;
+Object.defineProperty(this, "x", {value: 0, writable: false});
+
+for (var a = 0; a < 10; ++a)
+    r = ++x;
+assertEq(x, 0);
+assertEq(r, 1);
+
+for (var a = 0; a < 10; ++a)
+    r = --x;
+assertEq(x, 0);
+assertEq(r, -1);
+
+for (var a = 0; a < 10; ++a)
+    r = x++;
+assertEq(x, 0);
+assertEq(r, 0);
+
+for (var a = 0; a < 10; ++a)
+    r = x--;
+assertEq(x, 0);
+assertEq(r, 0);