diff --git a/cpdfcommand.ml b/cpdfcommand.ml
index c236f5c..9e09a5b 100644
--- a/cpdfcommand.ml
+++ b/cpdfcommand.ml
@@ -3593,6 +3593,11 @@ let print_version () =
   flprint
     ("cpdf " ^ (if agpl then "AGPL " else "") ^ "Version " ^ string_of_int major_version ^ "." ^ string_of_int minor_version ^ "." ^ string_of_int minor_minor_version ^ " " ^ version_date ^ "\n")
 
+let replace_obj pdf objspec obj =
+  let split_chain str = map (fun x -> "/" ^ x) (tl (String.split_on_char '/' str)) in
+  let chain = split_chain objspec in
+    Pdf.replace_chain pdf chain obj
+    
 (* Main function *)
 let go () =
   check_bookmarks_mistake ();
@@ -4637,7 +4642,7 @@ let go () =
   | Some (ReplaceObj (a, b)) ->
       let pdf = get_single_pdf args.op false in
       let pdfobj = Cpdfjson.object_of_json (Cpdfyojson.Safe.from_string b) in
-        Pdf.replace_obj pdf a pdfobj;
+        replace_obj pdf a pdfobj;
         write_pdf false pdf
   | Some (Verify standard) ->
       begin match standard with
diff --git a/cpdfdraw.ml b/cpdfdraw.ml
index e2e1d4c..da05783 100644
--- a/cpdfdraw.ml
+++ b/cpdfdraw.ml
@@ -770,7 +770,7 @@ let write_structure_tree pdf st =
            ("/K", Pdf.Array items)])
   in
     Pdf.addobj_given_num pdf (struct_tree_root, st);
-    Pdf.replace_chain pdf ["/Root"] ("/StructTreeRoot", Pdf.Indirect struct_tree_root)
+    Pdf.replace_chain pdf ["/Root"; "/StructTreeRoot"] (Pdf.Indirect struct_tree_root)
 
 let draw ~struct_tree ~fast ~underneath ~filename ~bates ~batespad range pdf drawops =
   (*Printf.printf "%s\n" (string_of_drawops drawops);*)
diff --git a/cpdfimage.ml b/cpdfimage.ml
index 4804e07..db6530b 100644
--- a/cpdfimage.ml
+++ b/cpdfimage.ml
@@ -533,7 +533,7 @@ let image_of_input ?subformat ?title ~process_struct_tree fobj i =
         Pdf.addobj_given_num pdf (figure, Pdf.Dictionary [("/K", Pdf.Array [Pdf.Integer 0]); ("/P", Pdf.Indirect document); ("/S", Pdf.Name "/Figure"); ("/Alt", Pdf.String title)]);
         Pdf.addobj_given_num pdf (str, Pdf.Dictionary [("/Namespaces", Pdf.Array [Pdf.Indirect namespace]); ("/Type", Pdf.Name "/StructTreeRoot");
                                                        ("/K", Pdf.Array [Pdf.Indirect document]); ("/ParentTree", Pdf.Indirect parent_tree)]);
-        Pdf.replace_chain pdf ["/Root"] ("/StructTreeRoot", (Pdf.Indirect str))
+        Pdf.replace_chain pdf ["/Root"; "/StructTreeRoot"] (Pdf.Indirect str)
       end
     else if process_struct_tree || subformat = Some Cpdfua.PDFUA1 then
       begin
@@ -543,7 +543,7 @@ let image_of_input ?subformat ?title ~process_struct_tree fobj i =
         Pdf.addobj_given_num pdf (parent_tree, Pdf.Dictionary [("/Nums", Pdf.Array [Pdf.Integer 1; Pdf.Array [Pdf.Indirect figure]])]);
         Pdf.addobj_given_num pdf (figure, Pdf.Dictionary [("/K", Pdf.Array [Pdf.Integer 0]); ("/P", Pdf.Indirect str); ("/S", Pdf.Name "/Figure"); ("/Alt", Pdf.String title)]);
         Pdf.addobj_given_num pdf (str, Pdf.Dictionary [("/Type", Pdf.Name "/StructTreeRoot"); ("/K", Pdf.Array [Pdf.Indirect figure]); ("/ParentTree", Pdf.Indirect parent_tree)]);
-        Pdf.replace_chain pdf ["/Root"] ("/StructTreeRoot", (Pdf.Indirect str))
+        Pdf.replace_chain pdf ["/Root"; "/StructTreeRoot"] (Pdf.Indirect str)
       end;
   let ops =
       (if structinfo then [Pdfops.Op_BDC ("/Figure", Pdf.Dictionary [("/MCID", Pdf.Integer 0)])] else [])
diff --git a/cpdfmetadata.ml b/cpdfmetadata.ml
index 1c9d159..da474eb 100644
--- a/cpdfmetadata.ml
+++ b/cpdfmetadata.ml
@@ -471,7 +471,7 @@ let language pdf =
   | _ -> None
 
 let set_language pdf s =
-  Pdf.replace_chain pdf ["/Root"] ("/Lang", (Pdf.String s))
+  Pdf.replace_chain pdf ["/Root"; "/Lang"] (Pdf.String s)
 
 let output_xmp_info ?(json=ref [("none", `Null)]) encoding pdf =
   let notjson = !json = [("none", `Null)] in
diff --git a/cpdftexttopdf.ml b/cpdftexttopdf.ml
index fc6358d..a2fb388 100644
--- a/cpdftexttopdf.ml
+++ b/cpdftexttopdf.ml
@@ -171,6 +171,6 @@ let typeset ~process_struct_tree ?subformat ?title ~papersize ~font ~fontsize te
             if subformat = Some Cpdfua.PDFUA2 then Pdf.Indirect document else Pdf.Array topks
           in
             Pdf.addobj_given_num pdf (str, Pdf.Dictionary (stns @ [("/Type", Pdf.Name "/StructTreeRoot"); ("/K", k); ("/ParentTree", Pdf.Indirect parent_tree)]));
-            Pdf.replace_chain pdf ["/Root"] ("/StructTreeRoot", (Pdf.Indirect str))
+            Pdf.replace_chain pdf ["/Root"; "/StructTreeRoot"] (Pdf.Indirect str)
         end;
         pdf
diff --git a/cpdfua.ml b/cpdfua.ml
index 11d108e..895e7d2 100644
--- a/cpdfua.ml
+++ b/cpdfua.ml
@@ -1610,8 +1610,8 @@ let create_pdfua1 title pagesize pages =
   let pdf = Cpdfmetadata.create_metadata pdf in
     Cpdfmetadata.set_language pdf "en-US";
     let pdf = Cpdfmetadata.set_viewer_preference ("/DisplayDocTitle", Pdf.Boolean true, 0) pdf in
-      Pdf.replace_obj pdf "/Root/MarkInfo/Marked" (Pdf.Boolean true);
-      Pdf.replace_obj pdf "/Root/StructTreeRoot/Type" (Pdf.Name "/StructTreeRoot");
+      Pdf.replace_chain pdf ["/Root"; "/MarkInfo"; "/Marked"] (Pdf.Boolean true);
+      Pdf.replace_chain pdf ["/Root"; "/StructTreeRoot"; "/Type"] (Pdf.Name "/StructTreeRoot");
       let pdf = {pdf with Pdf.major = 1; Pdf.minor =  7} in
         mark pdf;
         pdf
@@ -1622,8 +1622,8 @@ let create_pdfua2 title pagesize pages =
   let pdf = Cpdfmetadata.create_metadata pdf in
     Cpdfmetadata.set_language pdf "en-US";
     let pdf = Cpdfmetadata.set_viewer_preference ("/DisplayDocTitle", Pdf.Boolean true, 0) pdf in
-      Pdf.replace_obj pdf "/Root/MarkInfo/Marked" (Pdf.Boolean true);
-      Pdf.replace_obj pdf "/Root/StructTreeRoot/Type" (Pdf.Name "/StructTreeRoot");
+      Pdf.replace_chain pdf ["/Root"; "/MarkInfo"; "/Marked"] (Pdf.Boolean true);
+      Pdf.replace_chain pdf ["/Root"; "/StructTreeRoot"; "/Type"] (Pdf.Name "/StructTreeRoot");
       let pdf = {pdf with Pdf.major = 2; Pdf.minor =  0} in
         mark2 2024 pdf;
         pdf