Index: src/natools-s_expressions-generic_caches.adb
==================================================================
--- src/natools-s_expressions-generic_caches.adb
+++ src/natools-s_expressions-generic_caches.adb
@@ -114,11 +114,12 @@
                  Data => new Atom'(N.Data.all));
             when List_Node =>
                Result := new Node'(Kind => List_Node,
                  Parent => Parent,
                  Next => null,
-                 Child => Dup_List (N.Child, N));
+                 Child => null);
+               Result.Child := Dup_List (N.Child, Result);
          end case;
 
          if N = Source.Last then
             New_Last := Result;
          end if;