diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/for-of/arrays-growing-2.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/for-of/arrays-growing-2.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,10 @@
+// Inserting values in an array does not change the next index of an existing iterator.
+
+var a = [1, 2, 3, 4];
+var s = '';
+for (var v of a) {
+    s += v;
+    if (s.length === 2)
+        a.unshift('x');
+}
+assertEq(s, '12234');