diff --git a/modules/nix.nix b/modules/nix.nix
deleted file mode 100644
index 10c0692e..00000000
--- a/modules/nix.nix
+++ /dev/null
@@ -1,13 +0,0 @@
-{ pkgs, ... }:
-
-{
-  nix = {
-    package = with pkgs.nixVersions; nix_2_19;
-
-    settings = {
-      experimental-features = [ "nix-command" "flakes" "repl-flake" ];
-      auto-optimise-store = true;
-      warn-dirty = false;
-    };
-  };
-}
diff --git a/modules/system.nix b/modules/system.nix
index ad467e9f..46964b93 100644
--- a/modules/system.nix
+++ b/modules/system.nix
@@ -1,3 +1,8 @@
+{ pkgs, ... }:
+
+let
+  inherit (pkgs.nixVersions) nix_2_19;
+in
 {
   boot.loader = {
     systemd-boot = {
@@ -10,6 +15,21 @@
     efi.canTouchEfiVariables = true;
   };
 
+  systemd = {
+    extraConfig = "DefaultTimeoutStopSec=10s";
+    services.NetworkManager-wait-online.enable = false;
+  };
+
+  nix = {
+    package = nix_2_19;
+
+    settings = {
+      experimental-features = [ "nix-command" "flakes" "repl-flake" ];
+      auto-optimise-store = true;
+      warn-dirty = false;
+    };
+  };
+
   time.timeZone = "America/New_York";
 
   i18n.defaultLocale = "ja_JP.UTF-8";
diff --git a/modules/systemd.nix b/modules/systemd.nix
deleted file mode 100644
index 0bc00eed..00000000
--- a/modules/systemd.nix
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  systemd = {
-    extraConfig = "DefaultTimeoutStopSec=10s";
-    services.NetworkManager-wait-online.enable = false;
-  };
-}