diff --git a/cli/atom.ml b/cli/atom.ml
index af8978c..8fc209a 100644
--- a/cli/atom.ml
+++ b/cli/atom.ml
@@ -30,7 +30,7 @@ let htm_entry base_url text =
   "<entry><link rel=\"alternate\" href=\"" ^ base_url ^ "/" ^ u ^ ".htm\" />"
   ^ title text ^ id text ^ updated text ^ authors text
   ^ (opt_element "summary" @@ esc @@ Text.str "abstract" text)
-  ^ String_set.fold (fun elt a -> a ^ "<category term=\"" ^ elt ^ "\"/>") (Text.set "topics" text) ""
+  ^ String_set.fold (fun elt a -> a ^ "<category term=\"" ^ esc elt ^ "\"/>") (Text.set "topics" text) ""
   ^ "<content type=\"xhtml\"><div xmlns=\"http://www.w3.org/1999/xhtml\">"
   ^ P.of_string text.body ""
   ^ "</div></content></entry>\n"