A question about read syntax and compiled backreferences

[Juanma Barranquero]

Why can I evaluate this:

(defun test ()
 (let ((z '#1=(a b . #1#)))
   (safe-length z)))

but trying to loading it from a byte-compiled file brings

 Invalid read syntax: "#"

?

(I'm sure there's a simple explanation and I'm overlooking something...)

                   /L/e/k/t/u