diff --git a/cpdfmetadata.ml b/cpdfmetadata.ml
index 34e0e9e..f4849a5 100644
--- a/cpdfmetadata.ml
+++ b/cpdfmetadata.ml
@@ -56,11 +56,6 @@ let xmp_template =
 
 <?xpacket end='r'?>|}
 
-let pdfua_marker =
-{|<rdf:Description rdf:about="" xmlns:pdfuaid="http://www.aiim.org/pdfua/ns/id/">
-    <pdfuaid:part>1</pdfuaid:part>
-  </rdf:Description>"|}
-
 (* Set or replace metadata *)
 let set_metadata_from_bytes keepversion data pdf =
   let metadata_stream =
@@ -318,11 +313,11 @@ let bytes_of_xmltree t =
     Cpdfxmlm.output_doc_tree frag o t;
     bytes_of_string (Buffer.contents buf)
 
-(*let rec string_of_xmltree = function
+let rec string_of_xmltree = function
    D d ->
-     Printf.sprintf "DATA {%s}" d
+     Printf.sprintf "D {%s}" d
  | E (tag, trees) ->
-     Printf.sprintf "ELT (%s, %s)"
+     Printf.sprintf "E (%s, %s)"
        (string_of_tag tag)
        (string_of_xmltrees trees)
 
@@ -340,7 +335,7 @@ and string_of_attributes attrs =
 
 and string_of_xmltrees trees =
   fold_left
-    (fun a b -> a ^ " " ^ b) "" (map string_of_xmltree trees)*)
+    (fun a b -> a ^ " " ^ b) "" (map string_of_xmltree trees)
 
 let adobe = "http://ns.adobe.com/pdf/1.3/"
 let xmp = "http://ns.adobe.com/xap/1.0/"
diff --git a/cpdfmetadata.mli b/cpdfmetadata.mli
index c37d7fe..ebbda15 100644
--- a/cpdfmetadata.mli
+++ b/cpdfmetadata.mli
@@ -104,3 +104,7 @@ type xmltree =
 val xmltree_of_bytes : Pdfio.bytes -> Cpdfxmlm.dtd * xmltree
 
 val get_data_for : string -> string -> xmltree -> string option
+
+val string_of_xmltree : xmltree -> string
+
+val bytes_of_xmltree : Cpdfxmlm.dtd * xmltree -> Pdfio.bytes
diff --git a/cpdfua.ml b/cpdfua.ml
index a4fc429..80c9ae4 100644
--- a/cpdfua.ml
+++ b/cpdfua.ml
@@ -287,9 +287,34 @@ let test_matterhorn_json pdf =
         `Assoc [("name", `String name); ("section", `String section); ("error", `String error); ("extra", extra)])
       (test_matterhorn pdf))
 
+let pdfua_marker =
+  Cpdfmetadata.(E (((rdf, "Description"), [((rdf, "about"), ""); (("xmlns", "pdfuaid"), pdfuaid)]), [E (((pdfuaid, "part"), []), [D "1"])]))
+
+(*{|<rdf:Description rdf:about="" xmlns:pdfuaid="http://www.aiim.org/pdfua/ns/id/">
+    <pdfuaid:part>1</pdfuaid:part>
+  </rdf:Description>"|}*)
+
 let mark pdf =
   let pdf2 = if Cpdfmetadata.get_metadata pdf = None then Cpdfmetadata.create_metadata pdf else pdf in
    pdf.Pdf.objects <- pdf2.Pdf.objects;
    pdf.Pdf.trailerdict <- pdf2.Pdf.trailerdict;
-   pdf.Pdf.root <- pdf.Pdf.root;
-   ()
+   pdf.Pdf.root <- pdf2.Pdf.root;
+   match Cpdfmetadata.get_metadata pdf with
+   | Some metadata ->
+       let dtd, tree = Cpdfmetadata.xmltree_of_bytes metadata in
+         (*Printf.printf "string_of_metadata: %s\n" (Cpdfmetadata.string_of_xmltree tree);*)
+         begin match Cpdfmetadata.get_data_for Cpdfmetadata.pdfuaid "part" tree with
+         | Some _ -> () (* Already so marked. *)
+         | None ->
+             (* If not, add our pdfua_marker to the list *)
+             let newtree = tree in
+             (*Cpdfmetadata.(match tree with
+               | E (("rdf"*)
+             let newbytes = Cpdfmetadata.bytes_of_xmltree (dtd, newtree) in
+             (* Write the metadata stream back. *)
+             let pdf3 = Cpdfmetadata.set_metadata_from_bytes true newbytes pdf in
+               pdf.Pdf.objects <- pdf3.Pdf.objects;
+               pdf.Pdf.trailerdict <- pdf3.Pdf.trailerdict;
+               pdf.Pdf.root <- pdf3.Pdf.root
+         end
+   | None -> assert false