Access to Address conversion question

[jerry@jvdsys.nextjk.stuyts.nl (Jerry van Dijk)]

It might be just me again, but I cannot figure out how to convert an access 
type to an address, as in assigning Address_C in the code below. GNAT (3.03)
tells me I have an invalid parameter list in the call to To_Address here ?

Of course I realize that although my C background makes me view Some_Object_Ptr
as just an alias for Some_Object'ACCESS it is, in fact, a different type.

However, LRM 13.7.2 (3) led me to believe it should be possible... 

with System.Address_To_Access_Conversions;
with System.Storage_Elements; use System.Storage_Elements;

procedure Demo is

   type Some_Object is array (1..10) of Character;
   type Some_Object_Ptr is access all Some_Object;

   package Some_Object_Conversion is
      new System.Address_To_Access_Conversions(Some_Object);
   use Some_Object_Conversion;

   A_Object     : aliased Some_Object;
   A_Object_Ptr : Some_Object_Ptr := A_Object'ACCESS;

   Address_A, Address_B, Address_C : Integer;

begin
   Address_A := Integer(To_Integer(A_Object'ADDRESS));
   Address_B := Integer(To_Integer(To_Address(A_Object'ACCESS)));
   Address_C := Integer(To_Integer(To_Address(A_Object_Ptr)));
end Demo;

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