diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/bug642248.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/bug642248.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,10 @@
+function test(makeNonArray) {
+    function C() {}
+    C.prototype = []
+    c = new C();
+    c.push("foo");
+    return c.length
+}
+assertEq(test(true), 1);
+var a = [];
+var b = Object.create(a);