diff --git a/lisp/org-agenda.el b/lisp/org-agenda.el
index 65a9dfab6..1f96fa26c 100644
--- a/lisp/org-agenda.el
+++ b/lisp/org-agenda.el
@@ -4929,6 +4929,7 @@ the documentation of `org-diary'."
       (with-current-buffer buffer
 	(unless (derived-mode-p 'org-mode)
 	  (error "Agenda file %s is not in `org-mode'" file))
+	(setq org-agenda-buffer (or org-agenda-buffer buffer))
 	(let ((case-fold-search nil))
 	  (save-excursion
 	    (save-restriction