diff --git a/lisp/org-compat.el b/lisp/org-compat.el
index 60df315a5..aa0657358 100644
--- a/lisp/org-compat.el
+++ b/lisp/org-compat.el
@@ -1050,7 +1050,8 @@ key."
     ((guard (not (lookup-key calendar-mode-map "c")))
      (local-set-key "c" #'org-calendar-goto-agenda))
     (_ nil))
-  (unless (eq org-agenda-diary-file 'diary-file)
+  (unless (and (boundp 'org-agenda-diary-file)
+	       (eq org-agenda-diary-file 'diary-file))
     (local-set-key org-calendar-insert-diary-entry-key
 		   #'org-agenda-diary-entry)))