diff --git a/nix/modules/nixos/infrastructure/vault-server-approle/unix-user.nix b/nix/modules/nixos/infrastructure/vault-server-approle/unix-user.nix
index 6b0941e..bb777d6 100644
--- a/nix/modules/nixos/infrastructure/vault-server-approle/unix-user.nix
+++ b/nix/modules/nixos/infrastructure/vault-server-approle/unix-user.nix
@@ -11,7 +11,6 @@ let
   setKhsPassword = pkgs.writeShellApplication {
     name = "set-khs-password";
     runtimeInputs = [
-      pkgs.su
       pkgs.uutils-coreutils-noprefix
     ];
     text = ''
@@ -23,7 +22,7 @@ let
         exit 1
       fi
       hashed_passwd="$(cat /run/unix-users/khs)"
-      usermod --password "$hashed_passwd" khs
+      /run/current-system/sw/bin/usermod --password "$hashed_passwd" khs
     '';
   };
 in