Objective Caml version 3.09.2

# #directory "/Tools/ocaml/hweak-1.1/";;
# #load "hweak.cma";;
# let container = new Weak_memo.c 100;;
val container : < _.. > Weak_memo.c = <obj>
# class foo =
   object
   method foo = "foo!"
   end;;
class foo : object method foo : string end
# let foo1 = new foo;;
val foo1 : foo = <obj>
# let un_foo1 = (foo1 :> < >);;
val un_foo1 : <  > = <obj>
# container#add foo1;;
- : unit = ()
# container#find un_foo1;;
Exception: Not_found.

Color me confused.