diff --git a/hosts/Styx/configuration.nix b/hosts/Styx/configuration.nix
index b71f770..eda83da 100644
--- a/hosts/Styx/configuration.nix
+++ b/hosts/Styx/configuration.nix
@@ -1,6 +1,7 @@
 {
   inputs,
   pkgs,
+  config,
   ...
 }:
 
@@ -118,6 +119,16 @@
     server.port = 6742;
   };
 
+  # Windows' vendor RGB app tells the ARGB controllers to switch off before
+  # the system reaches S5; there's no equivalent on Linux, so without this the
+  # LEDs just retain their last state straight through poweroff/reboot.
+  # ExecStop runs while the openrgb SDK server (the service's main process) is
+  # still alive -- systemd waits for it to finish before killing the main
+  # process -- so this client call can still reach the server and switch every
+  # device off before the service, and the system, goes down.
+  systemd.services.openrgb.serviceConfig.ExecStop =
+    "${pkgs.openrgb-with-all-plugins}/bin/openrgb --mode off --client 127.0.0.1:${toString config.services.hardware.openrgb.server.port}";
+
   # The board's ACPI tables reserve I/O ports 0xB00-0xB0F for an OpRegion
   # (\GSA1.SMBI), which overlaps the AMD FCH SMBus controller's I/O range.
   # With strict ACPI resource enforcement (the default), the kernel refuses