diff --git a/flake.nix b/flake.nix
index 96b46c9..300dda6 100644
--- a/flake.nix
+++ b/flake.nix
@@ -10,51 +10,52 @@
     extra-substituters = [ "https://natsukagami.cachix.org" ];
     trusted-public-keys = [ "natsukagami.cachix.org-1:3U6GV8i8gWEaXRUuXd2S4ASfYgdl2QFPWg4BKPbmYiQ=" ];
   };
-  outputs = { self, nixpkgs, flake-utils, ... }@inputs: flake-utils.lib.eachDefaultSystem (system:
-    let
-      pkgs = import nixpkgs { inherit system; };
+  outputs = { self, nixpkgs, flake-utils, ... }@inputs: flake-utils.lib.eachDefaultSystem
+    (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
 
-      naersk = pkgs.callPackage inputs.naersk { };
-    in
-    rec {
-      packages.youmubot = pkgs.callPackage ./package.nix { inherit naersk; };
+        naersk = pkgs.callPackage inputs.naersk { };
+      in
+      rec {
+        packages.youmubot = pkgs.callPackage ./package.nix { inherit naersk; };
 
-      defaultPackage = packages.youmubot;
+        defaultPackage = packages.youmubot;
 
-      overlays.default = final: prev: {
-        youmubot = final.callPackage ./package.nix {
-          naersk = final.callPackage inputs.naersk { };
+        # `nix run`
+        apps.youmubot = flake-utils.lib.mkApp {
+          drv = packages.youmubot;
+          exePath = "/bin/youmubot";
         };
-      };
+        defaultApp = apps.youmubot;
 
-      # `nix run`
-      apps.youmubot = flake-utils.lib.mkApp {
-        drv = packages.youmubot;
-        exePath = "/bin/youmubot";
-      };
-      defaultApp = apps.youmubot;
+        # `nix develop`
+        devShell = pkgs.mkShell
+          {
+            buildInputs =
+              nixpkgs.lib.optionals pkgs.stdenv.isDarwin
+                (with pkgs; [
+                  libiconv
+                  darwin.apple_sdk.frameworks.Security
+                ])
+              ++ (with pkgs; [
+                openssl
+                cargo
+                rustfmt
+              ]);
 
-      # `nix develop`
-      devShell = pkgs.mkShell
-        {
-          buildInputs =
-            nixpkgs.lib.optionals pkgs.stdenv.isDarwin
-              (with pkgs; [
-                libiconv
-                darwin.apple_sdk.frameworks.Security
-              ])
-            ++ (with pkgs; [
-              openssl
-              cargo
-              rustfmt
+            nativeBuildInputs = nixpkgs.lib.optionals pkgs.stdenv.isLinux (with pkgs; [
+              pkg-config
             ]);
-
-          nativeBuildInputs = nixpkgs.lib.optionals pkgs.stdenv.isLinux (with pkgs; [
-            pkg-config
-          ]);
-        };
-      # module
-      nixosModule = import ./module.nix defaultPackage;
-    });
+          };
+      }) // {
+    overlays.default = final: prev: {
+      youmubot = final.callPackage ./package.nix {
+        naersk = final.callPackage inputs.naersk { };
+      };
+    };
+    # module
+    nixosModules.default = import ./module.nix;
+  };
 }
 
diff --git a/module.nix b/module.nix
index 720f11a..34ddac9 100644
--- a/module.nix
+++ b/module.nix
@@ -1,4 +1,4 @@
-youmubot: { config, pkgs, lib, ... }:
+{ config, pkgs, lib, ... }:
 
 with lib;
 let
@@ -7,10 +7,7 @@ in
 {
   options.services.youmubot = {
     enable = mkEnableOption "Enable youmubot, the discord bot made with Rust.";
-    package = mkOption {
-      type = types.package;
-      default = youmubot;
-    };
+    package = mkPackageOption pkgs "youmubot" { };
 
     envFile = mkOption {
       type = types.path;