diff --git a/cpdfannot.ml b/cpdfannot.ml
index 47f0837..d954756 100644
--- a/cpdfannot.ml
+++ b/cpdfannot.ml
@@ -152,8 +152,13 @@ let list_annotations_json range pdf =
          `List [`Int ~-n; Cpdfjson.json_of_object ~clean_strings:true pdf (fun _ -> ()) false false (Pdf.lookup_obj pdf n)])
       (setify (flatten (map (Pdf.objects_referenced [] [] pdf) extra)))
   in
-    Printf.printf "EXTRA: %i objects\n" (length extra);
-    let json = `List (json @ extra) in
+  let header =
+    `List
+     [`Int 0;
+      Cpdfjson.json_of_object ~clean_strings:true pdf (fun _ -> ()) false false
+        (Pdf.Dictionary ["/CPDFJSONannotformatversion", Pdf.Integer 1])]
+  in
+  let json = `List ([header] @ json @ extra) in
     J.pretty_to_channel stdout json
 
 let list_annotations ~json range encoding pdf =