diff --git a/mu4e/mu4e-icalendar.el b/mu4e/mu4e-icalendar.el
index 93da0faa..8813df61 100644
--- a/mu4e/mu4e-icalendar.el
+++ b/mu4e/mu4e-icalendar.el
@@ -172,13 +172,10 @@ response in icalendar format."
       ;; also trash the message (thus must be appended to hooks).
       (add-hook
        'message-sent-hook
-       #'mu4e~icalendar-setup-sent-hook-fn
+       (defun mu4e~icalendar-trash-hook()
+         (setq mu4e-sent-func (mu4e~icalendar-trash-message original-msg)))
        t t))))
 
-(defun mu4e~icalendar-setup-sent-hook-fn ()
-  (setq mu4e-sent-func
-        (mu4e~icalendar-trash-message original-msg)))
-
 (defun mu4e~icalendar-insert-diary (event reply-status filename)
   "Insert a diary entry for the EVENT in file named FILENAME.
 REPLY-STATUS is the status of the reply.  The possible values are