diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/for-of/array-holes-5.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/for-of/array-holes-5.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,6 @@
+// for-of does not skip trailing holes; the value is undefined.
+
+var log = "";
+for (var x of [1, 2, 3,,])
+    log += x;
+assertEq(log, "123undefined");