diff --git a/nixbld-etc-nixos/backup-module.nix b/nixbld-etc-nixos/backup-module.nix
index 2c743e9..9206b85 100644
--- a/nixbld-etc-nixos/backup-module.nix
+++ b/nixbld-etc-nixos/backup-module.nix
@@ -52,7 +52,7 @@ in
     systemd.timers.mlabs-backup = {
       description = "M-Labs backup";
       wantedBy = [ "timers.target" ];
-      timerConfig.OnCalendar = "tuesday,friday";
+      timerConfig.OnCalendar = "tuesday,friday *-*-* 08:00:00";
     };
   };
 }