diff -r 66a8113ac23e -r bcecb69f72fa src/Pure/PIDE/markup.ML
--- a/src/Pure/PIDE/markup.ML	Thu Aug 29 11:43:14 2024 +0200
+++ b/src/Pure/PIDE/markup.ML	Thu Aug 29 17:47:29 2024 +0200
@@ -864,8 +864,8 @@
 val enclose = output #-> Library.enclose;
 
 fun markup m =
-  let val (bg, en) = output m
-  in Library.enclose (Output.escape bg) (Output.escape en) end;
+  let val (bg, en) = output m |> apply2 (single #> Output.escape #> implode);
+  in Library.enclose bg en end;
 
 val markups = fold_rev markup;