src/Pure/PIDE/document.ML

     | Header header =>
         let
           val imports = (case header of Exn.Res (_, {imports, ...}) => imports | _ => []);
           val keywords = (case header of Exn.Res (_, {keywords, ...}) => keywords | _ => []);
           val header' =
-            (List.app Keyword.declare keywords; header)
+            (List.app (fn (name, decl) =>
+                Keyword.declare name (Option.map Keyword.make decl)) keywords; header)
               handle exn as ERROR _ => Exn.Exn exn;
           val nodes1 = nodes
             |> default_node name
             |> fold default_node imports;
           val nodes2 = nodes1