diff --git a/lisp/gnus/gnus-icalendar.el b/lisp/gnus/gnus-icalendar.el
index 1e0e2071018..9811e8b440f 100644
--- a/lisp/gnus/gnus-icalendar.el
+++ b/lisp/gnus/gnus-icalendar.el
@@ -835,6 +835,7 @@ These will be used to retrieve the RSVP information from ical events."
        keymap ,gnus-mime-button-map
        face ,gnus-article-button-face
        follow-link t
+       category t
        button t
        gnus-data ,data))))