Index: src/natools-s_expressions-generic_caches.adb
==================================================================
--- src/natools-s_expressions-generic_caches.adb
+++ src/natools-s_expressions-generic_caches.adb
@@ -420,6 +420,12 @@
 
       Object.Locked
         := Object.Absolute_Level < Lockable.Current_Level (Object.Stack);
    end Unlock;
 
+
+   overriding function Duplicate (Object : Cursor) return Cursor is
+   begin
+      return Object;
+   end Duplicate;
+
 end Natools.S_Expressions.Generic_Caches;

Index: src/natools-s_expressions-generic_caches.ads
==================================================================
--- src/natools-s_expressions-generic_caches.ads
+++ src/natools-s_expressions-generic_caches.ads
@@ -28,10 +28,11 @@
 
 with System.Storage_Pools;
 
 with Natools.S_Expressions.Lockable;
 with Natools.S_Expressions.Printers;
+with Natools.S_Expressions.Replayable;
 
 private with Ada.Finalization;
 private with Ada.Unchecked_Deallocation;
 private with Natools.References;
 
@@ -53,11 +54,12 @@
 
    function Duplicate (Cache : Reference) return Reference;
       --  Create a new copy of the S-expression held in Cache and return it
 
 
-   type Cursor is new Lockable.Descriptor with private;
+   type Cursor is new Lockable.Descriptor and Replayable.Descriptor
+     with private;
    pragma Preelaborable_Initialization (Cursor);
 
    overriding function Current_Event (Object : in Cursor) return Events.Event;
    overriding function Current_Atom (Object : in Cursor) return Atom;
    overriding function Current_Level (Object : in Cursor) return Natural;
@@ -77,10 +79,12 @@
       State : out Lockable.Lock_State);
    overriding procedure Unlock
      (Object : in out Cursor;
       State : in out Lockable.Lock_State;
       Finish : in Boolean := True);
+
+   overriding function Duplicate (Object : Cursor) return Cursor;
 
    function First (Cache : Reference'Class) return Cursor;
       --  Create a new Cursor pointing at the beginning of Cache
 
 private
@@ -141,11 +145,11 @@
    type Reference is new Printers.Printer with record
       Exp : Trees.Reference;
    end record;
 
 
-   type Cursor is new Lockable.Descriptor with record
+   type Cursor is new Lockable.Descriptor and Replayable.Descriptor with record
       Exp : Trees.Reference;
       Position : Node_Access := null;
       Opening : Boolean := False;
       Stack : Lockable.Lock_Stack;
       Locked : Boolean := False;