diff --git a/operating-systems/buer/shepherd-services.scm b/operating-systems/buer/shepherd-services.scm
index a31da28..bec1ece 100644
--- a/operating-systems/buer/shepherd-services.scm
+++ b/operating-systems/buer/shepherd-services.scm
@@ -43,11 +43,13 @@ next calendar event.")))
                                #:hours '(8 14 20)
                                #:minutes '(0))
                (lambda ()
-                 (let ((btrfs "/run/current-system/profile/bin/btrfs")
-                       (date (strftime "%Y-%m-%d" (localtime (current-time)))))
-                   (spawn-shell-command
-                     (string-append btrfs " subvolume snapshot"
-                                    " /home /snapshots/home/" date))))))
+                 (let* ((btrfs "/run/current-system/profile/bin/btrfs")
+                        (date (strftime "%Y-%m-%d" (localtime (current-time))))
+                        (snapshot (string-append "/snapshots/home/" date)))
+                   (unless (file-exists? snapshot)
+                     (spawn-shell-command
+                       (string-join
+                         `(btrfs "subvolume snapshot /home" snapshot))))))))
     (stop #~(make-timer-destructor))
     (actions (list timer-trigger-action))))