diff --git a/asus/battery.nix b/asus/battery.nix
index 4bdf6b649..4639baa49 100644
--- a/asus/battery.nix
+++ b/asus/battery.nix
@@ -6,7 +6,8 @@
 }:
 let
   p = pkgs.writeScriptBin "charge-upto" ''
-    echo ''${0:-100} > /sys/class/power_supply/BAT?/charge_control_end_threshold
+    #!${pkgs.bash}/bin/bash
+    echo ''${1:-100} > /sys/class/power_supply/BAT?/charge_control_end_threshold
   '';
   cfg = config.hardware.asus.battery;
 in