diff --git a/nixops/avscan-module.nix b/nixops/avscan-module.nix
index f8e6864f..4104ced7 100644
--- a/nixops/avscan-module.nix
+++ b/nixops/avscan-module.nix
@@ -39,7 +39,7 @@ in
     systemd.timers.avscan = {
       description = "Antivirus scan";
       wantedBy = [ "timers.target" ];
-      timerConfig.OnCalendar = "Mon 13:00";
+      timerConfig.OnCalendar = "Mon *-*-* 13:00:00";
     };
   };
 }