diff --git a/flake.nix b/flake.nix
index 06a1d10..42a9a01 100644
--- a/flake.nix
+++ b/flake.nix
@@ -13,49 +13,53 @@
     extra-substituters = [ "https://natsukagami.cachix.org" ];
     trusted-public-keys = [ "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=" "natsukagami.cachix.org-1:3U6GV8i8gWEaXRUuXd2S4ASfYgdl2QFPWg4BKPbmYiQ=" ];
   };
-  outputs = { self, nixpkgs, flake-utils, ... }@inputs: flake-utils.lib.eachDefaultSystem
-    (system:
-      let
-        pkgs = import nixpkgs
-          {
-            inherit system; overlays = [ (import inputs.rust-overlay) ];
+  outputs = { self, nixpkgs, flake-utils, ... }@inputs:
+    let
+      rustVersion = "1.83.0";
+    in
+    flake-utils.lib.eachDefaultSystem
+      (system:
+        let
+          pkgs = import nixpkgs
+            {
+              inherit system; overlays = [ (import inputs.rust-overlay) ];
+            };
+          craneLib = (inputs.crane.mkLib pkgs).overrideToolchain (p: p.rust-bin.stable.${rustVersion}.default);
+          # craneLib = inputs.crane.mkLib pkgs;
+        in
+        rec {
+          packages.youmubot = pkgs.callPackage ./package.nix { inherit craneLib; };
+
+          defaultPackage = packages.youmubot;
+
+          # `nix run`
+          apps.youmubot = flake-utils.lib.mkApp {
+            drv = packages.youmubot;
+            exePath = "/bin/youmubot";
           };
-        craneLib = (inputs.crane.mkLib pkgs).overrideToolchain (p: p.rust-bin.stable."1.83.0".default);
-        # craneLib = inputs.crane.mkLib pkgs;
-      in
-      rec {
-        packages.youmubot = pkgs.callPackage ./package.nix { inherit craneLib; };
+          defaultApp = apps.youmubot;
 
-        defaultPackage = packages.youmubot;
+          # `nix develop`
+          devShell = pkgs.mkShell
+            {
+              inputsFrom = [ packages.youmubot ];
 
-        # `nix run`
-        apps.youmubot = flake-utils.lib.mkApp {
-          drv = packages.youmubot;
-          exePath = "/bin/youmubot";
+              buildInputs = with pkgs; [ rustfmt clippy sqlx-cli rust-analyzer ];
+
+              nativeBuildInputs = nixpkgs.lib.optionals pkgs.stdenv.isLinux (with pkgs; [
+                pkg-config
+              ]);
+
+              RUST_SRC_PATH = pkgs.rustPlatform.rustLibSrc;
+            };
+        }) // {
+      overlays.default = final: prev: {
+        youmubot = final.callPackage ./package.nix {
+          craneLib = (inputs.crane.mkLib final).overrideToolchain (p: p.rust-bin.stable.${rustVersion}.default);
         };
-        defaultApp = apps.youmubot;
-
-        # `nix develop`
-        devShell = pkgs.mkShell
-          {
-            inputsFrom = [ packages.youmubot ];
-
-            buildInputs = with pkgs; [ rustfmt clippy sqlx-cli rust-analyzer ];
-
-            nativeBuildInputs = nixpkgs.lib.optionals pkgs.stdenv.isLinux (with pkgs; [
-              pkg-config
-            ]);
-
-            RUST_SRC_PATH = pkgs.rustPlatform.rustLibSrc;
-          };
-      }) // {
-    overlays.default = final: prev: {
-      youmubot = final.callPackage ./package.nix {
-        craneLib = (inputs.crane.mkLib final).overrideToolchain (p: p.rust-bin.stable."1.79.0".default);
       };
+      # module
+      nixosModules.default = import ./module.nix;
     };
-    # module
-    nixosModules.default = import ./module.nix;
-  };
 }