src/Pure/General/name_space.ML

     | NONE =>
         let
           val completions = map (fn pos => completion context space (xname, pos)) ps;
         in
           error (undefined (kind_of space) name ^ Position.here_list ps ^
-            implode (map (Markup.markup_report o Completion.reported_text) completions))
+            Markup.markup_report (implode (map Completion.reported_text completions)))
         end)
   end;
 
 fun check context table (xname, pos) =
   let