diff --git a/cpdfcommand.ml b/cpdfcommand.ml
index bc3ab02..67b009e 100644
--- a/cpdfcommand.ml
+++ b/cpdfcommand.ml
@@ -4544,7 +4544,7 @@ let go () =
           let range = parse_pagespec_allow_empty pdf (get_pagespec ()) in
             let pdf =
               Cpdfpage.stamp
-                args.relative_to_cropbox args.position args.topline args.midline args.fast
+                ~process_struct_tree:args.process_struct_trees args.relative_to_cropbox args.position args.topline args.midline args.fast
                 args.scale_stamp_to_fit true range overpdf pdf
             in
               write_pdf false pdf
@@ -4558,7 +4558,7 @@ let go () =
           let range = parse_pagespec_allow_empty pdf (get_pagespec ()) in
             let pdf =
               Cpdfpage.stamp
-                args.relative_to_cropbox args.position args.topline args.midline args.fast
+                ~process_struct_tree:args.process_struct_trees args.relative_to_cropbox args.position args.topline args.midline args.fast
                 args.scale_stamp_to_fit false range underpdf pdf
             in
               write_pdf false pdf
@@ -4569,6 +4569,7 @@ let go () =
         warn_prerotate (parse_pagespec overpdf "all") overpdf;
         write_pdf false
           (Cpdfpage.combine_pages
+             ~process_struct_tree:args.process_struct_trees
              args.fast
                (prerotate (parse_pagespec underpdf "all") underpdf)
                (prerotate (parse_pagespec overpdf "all") overpdf)
diff --git a/cpdfpage.ml b/cpdfpage.ml
index f957832..c29a763 100644
--- a/cpdfpage.ml
+++ b/cpdfpage.ml
@@ -803,7 +803,7 @@ let do_stamp relative_to_cropbox fast position topline midline scale_to_fit isov
          Pdfpage.resources =
            Pdfpage.combine_pdf_resources pdf u.Pdfpage.resources o.Pdfpage.resources}
 
-let stamp relative_to_cropbox position topline midline fast scale_to_fit isover range over pdf =
+let stamp ~process_struct_tree relative_to_cropbox position topline midline fast scale_to_fit isover range over pdf =
   let prefix = Pdfpage.shortest_unused_prefix pdf in
   Pdfpage.add_prefix over prefix;
   let marks = Pdfmarks.read_bookmarks pdf in
@@ -875,7 +875,7 @@ let equalize_pages under over =
     else
       under, over
 
-let combine_pages fast under over scaletofit swap equalize =
+let combine_pages ~process_struct_tree fast under over scaletofit swap equalize =
   let debug_combine_pages = false in
   let debug_pdf pdf n =
     if debug_combine_pages then
diff --git a/cpdfpage.mli b/cpdfpage.mli
index 17ac14d..d097e17 100644
--- a/cpdfpage.mli
+++ b/cpdfpage.mli
@@ -91,12 +91,12 @@ the same number of pages as the shorter file. If [scaletofit] is true, the
 [over] file will be scaled to fit. If [swap] is true, [over] and [under] are
 swapped.  If [fast] is true, the PDFs are assumed to be well-formed and no
 fixes are done. *)
-val combine_pages : bool -> Pdf.t -> Pdf.t -> bool -> bool -> bool -> Pdf.t
+val combine_pages : process_struct_tree:bool -> bool -> Pdf.t -> Pdf.t -> bool -> bool -> bool -> Pdf.t
 
 (** [stamp relative_to_cropbox position topline midline fast scale_to_fit isover range over pdf] stamps the first page of
 [over] over each page of the PDF. The arguments have the same meaning as in
 [combine_pages]. *)
-val stamp : bool -> Cpdfposition.position -> bool -> bool -> bool -> bool -> bool -> int list -> Pdf.t -> Pdf.t -> Pdf.t
+val stamp : process_struct_tree:bool -> bool -> Cpdfposition.position -> bool -> bool -> bool -> bool -> bool -> int list -> Pdf.t -> Pdf.t -> Pdf.t
 
 (**  {2 Page geometry} *)