diff --git a/modules/spin-down.nix b/modules/spin-down.nix
index bce8b9f..c2d2764 100644
--- a/modules/spin-down.nix
+++ b/modules/spin-down.nix
@@ -56,6 +56,11 @@
 #   # -i 120: Spin down after 2 minutes (120 seconds) of inactivity.
 #   ExecStart = "${pkgs.hd-idle}/bin/hd-idle -a /dev/disk/by-id/XXX-XXX-XXX -i 120";
 
+# Note about the `script` settings below.
+# If the disk is spun-down (in standby mode):
+# - The standby timeout has been set before already, otherwise it would be spinning.
+# - Don't set the standby timeout again, as this will spin up the disk.
+
 {
   environment.systemPackages = with pkgs; [
     hdparm
@@ -63,25 +68,25 @@
   systemd.services."hdparm-4tb1" = {
     description = "Spin down inactive HDD";
     wantedBy = [ "multi-user.target" ];
-    serviceConfig = {
-      Type = "oneshot";
-      ExecStart = "${pkgs.hdparm}/bin/hdparm -S 24 /dev/disk/by-id/ata-WDC_WD40EFRX-68N32N0_WD-WCC7K0CPF0N1";
-    };
+    serviceConfig.Type = "oneshot";
+    script = ''
+      ${pkgs.hdparm}/bin/hdparm -C /dev/disk/by-id/ata-WDC_WD40EFRX-68N32N0_WD-WCC7K0CPF0N1 | ${pkgs.busybox}/bin/grep 'standby' || ${pkgs.hdparm}/bin/hdparm -S 24 /dev/disk/by-id/ata-WDC_WD40EFRX-68N32N0_WD-WCC7K0CPF0N1
+    '';
   };
   systemd.services."hdparm-3tb1" = {
     description = "Spin down inactive HDD";
     wantedBy = [ "multi-user.target" ];
-    serviceConfig = {
-      Type = "oneshot";
-      ExecStart = "${pkgs.hdparm}/bin/hdparm -S 24 /dev/disk/by-id/ata-WDC_WD30EFRX-68EUZN0_WD-WCC4N1173157";
-    };
+    serviceConfig.Type = "oneshot";
+    script = ''
+      ${pkgs.hdparm}/bin/hdparm -C /dev/disk/by-id/ata-WDC_WD30EFRX-68EUZN0_WD-WCC4N1173157 | ${pkgs.busybox}/bin/grep 'standby' || ${pkgs.hdparm}/bin/hdparm -S 24 /dev/disk/by-id/ata-WDC_WD30EFRX-68EUZN0_WD-WCC4N1173157
+    '';
   };
   systemd.services."hdparm-3tb2" = {
     description = "Spin down inactive HDD";
     wantedBy = [ "multi-user.target" ];
-    serviceConfig = {
-      Type = "oneshot";
-      ExecStart = "${pkgs.hdparm}/bin/hdparm -S 24 /dev/disk/by-id/ata-WDC_WD30EFRX-68EUZN0_WD-WMC4N0564095";
-    };
+    serviceConfig.Type = "oneshot";
+    script = ''
+      ${pkgs.hdparm}/bin/hdparm -C /dev/disk/by-id/ata-WDC_WD30EFRX-68EUZN0_WD-WMC4N0564095 | ${pkgs.busybox}/bin/grep 'standby' || ${pkgs.hdparm}/bin/hdparm -S 24 /dev/disk/by-id/ata-WDC_WD30EFRX-68EUZN0_WD-WMC4N0564095
+    '';
   };
 }