diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testLengthOnNonNativeProto.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testLengthOnNonNativeProto.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,20 @@
+function testLengthOnNonNativeProto()
+{
+  var o = {};
+  o.__proto__ = [3];
+  for (var j = 0; j < 5; j++)
+    o[0];
+
+  var o2 = {};
+  o2.__proto__ = [];
+  for (var j = 0; j < 5; j++)
+    o2.length;
+
+  function foo() { }
+  foo.__proto__ = [];
+  for (var j = 0; j < 5; j++)
+    foo.length;
+
+  return "no assertion";
+}
+assertEq(testLengthOnNonNativeProto(), "no assertion");