diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/collections/Map-iterator-add-remove.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/collections/Map-iterator-add-remove.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,14 @@
+// Removing and re-adding entries while an iterator is live causes the iterator to visit them again.
+
+var map = Map([['a', 1]]);
+var n = 5;
+for (let [k, v] of map) {
+    assertEq(k, 'a');
+    assertEq(v, 1);
+    if (n === 0)
+        break;
+    map.delete('a');
+    map.set('a', 1);
+    n--;
+}
+assertEq(n, 0);