diff --git a/bin/deploy b/bin/deploy
index 0928d8b2a7057dfc35e3dd42dfcfca370ee7adbc..8ffccf5262d6c1f83ad6cab9292e26cdafb2b03b 100755
--- a/bin/deploy
+++ b/bin/deploy
@@ -8,8 +8,8 @@ set -o pipefail
 readonly cmdname=$(basename $0)
 
 
-nixos_system_file=$MACHINES_PATH/nixos.nix
-nixos_iso_file=$MACHINES_PATH/nixos_iso.nix
+readonly nixos_system_file=$MACHINES_PATH/nixos.nix
+readonly nixos_iso_file=$MACHINES_PATH/nixos_iso.nix
 
 # This script cannot run without the nixos configuration entry point
 if [[ ! -f "$nixos_system_file" ]]