src/Pure/ML/ml_antiquotations.ML

                 Completion.make (name, pos) (fn completed =>
                     Options.names (Options.default ())
                     |> filter completed
                     |> map (fn a => (a, ("system_option", a))));
               val report = Markup.markup_report (Completion.reported_text completion);
-            in cat_error msg report end;
+            in error (msg ^ report) end;
         val _ = Context_Position.report ctxt pos markup;
       in ML_Syntax.print_string name end)) #>
 
   ML_Antiquotation.value @{binding theory}
     (Args.context -- Scan.lift (Parse.position Args.name) >> (fn (ctxt, (name, pos)) =>