diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/bug640993.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/bug640993.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,7 @@
+function f() {
+    return f;
+}
+f.__proto__ = null;
+gc();
+f();
+new f();