diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testLengthInString.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testLengthInString.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,12 @@
+function testLengthInString()
+{
+  var s = new String();
+  var res = "length" in s;
+  for (var i = 0; i < 5; i++)
+    res = res && ("length" in s);
+  res = res && s.hasOwnProperty("length");
+  for (var i = 0; i < 5; i++)
+    res = res && s.hasOwnProperty("length");
+  return res;
+}
+assertEq(testLengthInString(), true);