diff --git a/flake.lock b/flake.lock
index 7765c01..f84e5f5 100644
--- a/flake.lock
+++ b/flake.lock
@@ -34,24 +34,6 @@
         "type": "github"
       }
     },
-    "flake-utils_2": {
-      "inputs": {
-        "systems": "systems_2"
-      },
-      "locked": {
-        "lastModified": 1731533236,
-        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
-    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1781074563,
@@ -71,7 +53,7 @@
     "nixpkgs-ruby": {
       "inputs": {
         "flake-compat": "flake-compat",
-        "flake-utils": "flake-utils_2",
+        "flake-utils": "flake-utils",
         "nixpkgs": [
           "nixpkgs"
         ]
@@ -92,9 +74,9 @@
     },
     "root": {
       "inputs": {
-        "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs",
-        "nixpkgs-ruby": "nixpkgs-ruby"
+        "nixpkgs-ruby": "nixpkgs-ruby",
+        "systems": "systems_2"
       }
     },
     "systems": {
diff --git a/flake.nix b/flake.nix
index 8e2044c..34c1ed5 100644
--- a/flake.nix
+++ b/flake.nix
@@ -5,7 +5,7 @@
     nixpkgs-ruby.url = "github:bobvanderlinden/nixpkgs-ruby";
     nixpkgs-ruby.inputs.nixpkgs.follows = "nixpkgs";
 
-    flake-utils.url = "github:numtide/flake-utils";
+    systems.url = "github:nix-systems/default";
   };
 
   outputs =
@@ -13,218 +13,227 @@
       self,
       nixpkgs,
       nixpkgs-ruby,
-      flake-utils,
+      systems,
     }:
-    flake-utils.lib.eachDefaultSystem (
-      system:
-      let
-        pkgs = nixpkgs.legacyPackages.${system};
-        lib = pkgs.lib;
-
-        defaultGroups = [
-          "default"
-          "production"
-          "development"
-          "test"
-        ];
-
-        gemsets =
-          let
-            entries = if builtins.pathExists ./gemsets then builtins.readDir ./gemsets else { };
-            dirs = lib.filterAttrs (_name: type: type == "directory") entries;
-          in
-          lib.mapAttrs (name: _type: {
-            path = ./gemsets/${name};
-            groups = defaultGroups;
-          }) dirs;
-
-        mkRuby =
-          name: cfg:
-          let
-            ruby = nixpkgs-ruby.lib.packageFromRubyVersionFile {
-              file = "${cfg.path}/ruby-version";
-              inherit system;
-            };
+    let
+      lib = nixpkgs.lib;
+      forEachSystem = lib.genAttrs (import systems);
+
+      perSystem = forEachSystem (
+        system:
+        let
+          pkgs = nixpkgs.legacyPackages.${system};
+
+          defaultGroups = [
+            "default"
+            "production"
+            "development"
+            "test"
+          ];
 
-            gems = pkgs.bundlerEnv {
-              name = "ruby-gemset-${name}";
-              inherit ruby;
-              gemfile = "${cfg.path}/Gemfile";
-              lockfile = "${cfg.path}/Gemfile.lock";
-              gemset = "${cfg.path}/gemset.nix";
-              groups = cfg.groups;
-            };
-          in
-          gems.wrappedRuby;
-
-        rubies = lib.mapAttrs mkRuby gemsets;
-
-        mkRubyApp = _name: ruby: {
-          type = "app";
-          program = "${ruby}/bin/ruby";
-        };
-
-        mkBundleApp =
-          name: ruby:
-          let
-            script = pkgs.writeShellScriptBin "bundle-${name}" ''
-              set -euo pipefail
-              export BUNDLE_GEMFILE="$PWD/gemsets/${name}/Gemfile"
-              exec ${ruby}/bin/bundle "$@"
-            '';
-          in
-          {
+          gemsets =
+            let
+              entries = if builtins.pathExists ./gemsets then builtins.readDir ./gemsets else { };
+              dirs = lib.filterAttrs (_name: type: type == "directory") entries;
+            in
+            lib.mapAttrs (name: _type: {
+              path = ./gemsets/${name};
+              groups = defaultGroups;
+            }) dirs;
+
+          mkRuby =
+            name: cfg:
+            let
+              ruby = nixpkgs-ruby.lib.packageFromRubyVersionFile {
+                file = "${cfg.path}/ruby-version";
+                inherit system;
+              };
+
+              gems = pkgs.bundlerEnv {
+                name = "ruby-gemset-${name}";
+                inherit ruby;
+                gemfile = "${cfg.path}/Gemfile";
+                lockfile = "${cfg.path}/Gemfile.lock";
+                gemset = "${cfg.path}/gemset.nix";
+                groups = cfg.groups;
+              };
+            in
+            gems.wrappedRuby;
+
+          rubies = lib.mapAttrs mkRuby gemsets;
+
+          mkRubyApp = _name: ruby: {
             type = "app";
-            program = "${script}/bin/bundle-${name}";
+            program = "${ruby}/bin/ruby";
           };
 
-        helper = pkgs.writeShellApplication {
-          name = "gemset";
-          runtimeInputs = [
-            pkgs.bundler
-            pkgs.bundix
-            pkgs.git
-          ];
-
-          text = ''
-            usage() {
-              cat <<EOF
-            Usage:
-              nix run .#gemset-create -- NAME [RUBY_VERSION]
-              nix run .#gemset-delete -- NAME
-              nix run .#gemset-lock   -- NAME
-              nix run .#gemset-update -- NAME
-
-            Gemset layout:
-              gemsets/NAME/Gemfile
-              gemsets/NAME/Gemfile.lock
-              gemsets/NAME/gemset.nix
-              gemsets/NAME/ruby-version
-            EOF
-            }
-
-            cmd="''${1:-}"
-            name="''${2:-}"
-            ruby_version="''${3:-3.3.6}"
-
-            [ -n "$cmd" ] && [ -n "$name" ] || {
-              usage
-              exit 1
-            }
-
-            case "$name" in
-              */*) echo "error: NAME must not contain slashes" >&2; exit 1 ;;
-            esac
-
-            dir="gemsets/$name"
-
-            case "$cmd" in
-              create)
-                mkdir -p "$dir"
-
-                if [ ! -f "$dir/ruby-version" ]; then
-                  printf '%s\n' "$ruby_version" > "$dir/ruby-version"
-                fi
-
-                if [ ! -f "$dir/Gemfile" ]; then
-                  cat > "$dir/Gemfile" <<'EOF'
-            source "https://rubygems.org"
-
-            # gem "rake"
-            EOF
-                fi
-
-                touch "$dir/Gemfile.lock"
-
-                if [ ! -f "$dir/gemset.nix" ]; then
-                  printf '{ }\n' > "$dir/gemset.nix"
-                fi
-
-                echo "Created $dir"
-                echo "Run: git add $dir"
-                echo "Then: nix develop .#$name"
-                ;;
-
-              delete)
-                rm -rf "$dir"
-                echo "Deleted $dir"
-                echo "Remove it from Git with: git add -A $dir"
-                ;;
-
-              lock)
-                cd "$dir"
-                bundle lock
-                bundix
-                echo "Updated $dir/Gemfile.lock and $dir/gemset.nix"
-                ;;
+          mkBundleApp =
+            name: ruby:
+            let
+              script = pkgs.writeShellScriptBin "bundle-${name}" ''
+                set -euo pipefail
+                export BUNDLE_GEMFILE="$PWD/gemsets/${name}/Gemfile"
+                exec ${ruby}/bin/bundle "$@"
+              '';
+            in
+            {
+              type = "app";
+              program = "${script}/bin/bundle-${name}";
+            };
 
-              update)
-                cd "$dir"
-                bundle update
-                bundix
-                echo "Updated $dir/Gemfile.lock and $dir/gemset.nix"
-                ;;
+          helper = pkgs.writeShellApplication {
+            name = "gemset";
+            runtimeInputs = [
+              pkgs.bundler
+              pkgs.bundix
+              pkgs.git
+            ];
 
-              *)
+            text = ''
+              usage() {
+                cat <<EOF
+              Usage:
+                nix run .#gemset-create -- NAME [RUBY_VERSION]
+                nix run .#gemset-delete -- NAME
+                nix run .#gemset-lock   -- NAME
+                nix run .#gemset-update -- NAME
+
+              Gemset layout:
+                gemsets/NAME/Gemfile
+                gemsets/NAME/Gemfile.lock
+                gemsets/NAME/gemset.nix
+                gemsets/NAME/ruby-version
+              EOF
+              }
+
+              cmd="''${1:-}"
+              name="''${2:-}"
+              ruby_version="''${3:-3.3.6}"
+
+              [ -n "$cmd" ] && [ -n "$name" ] || {
                 usage
                 exit 1
-                ;;
-            esac
-          '';
-        };
-
-        mkHelperApp =
-          subcommand:
-          let
-            script = pkgs.writeShellScriptBin "gemset-${subcommand}" ''
-              exec ${helper}/bin/gemset ${subcommand} "$@"
+              }
+
+              case "$name" in
+                */*) echo "error: NAME must not contain slashes" >&2; exit 1 ;;
+              esac
+
+              dir="gemsets/$name"
+
+              case "$cmd" in
+                create)
+                  mkdir -p "$dir"
+
+                  if [ ! -f "$dir/ruby-version" ]; then
+                    printf '%s\n' "$ruby_version" > "$dir/ruby-version"
+                  fi
+
+                  if [ ! -f "$dir/Gemfile" ]; then
+                    cat > "$dir/Gemfile" <<'EOF'
+              source "https://rubygems.org"
+
+              # gem "rake"
+              EOF
+                  fi
+
+                  touch "$dir/Gemfile.lock"
+
+                  if [ ! -f "$dir/gemset.nix" ]; then
+                    printf '{ }\n' > "$dir/gemset.nix"
+                  fi
+
+                  echo "Created $dir"
+                  echo "Run: git add $dir"
+                  echo "Then: nix develop .#$name"
+                  ;;
+
+                delete)
+                  rm -rf "$dir"
+                  echo "Deleted $dir"
+                  echo "Remove it from Git with: git add -A $dir"
+                  ;;
+
+                lock)
+                  cd "$dir"
+                  bundle lock
+                  bundix
+                  echo "Updated $dir/Gemfile.lock and $dir/gemset.nix"
+                  ;;
+
+                update)
+                  cd "$dir"
+                  bundle update
+                  bundix
+                  echo "Updated $dir/Gemfile.lock and $dir/gemset.nix"
+                  ;;
+
+                *)
+                  usage
+                  exit 1
+                  ;;
+              esac
             '';
-          in
-          {
-            type = "app";
-            program = "${script}/bin/gemset-${subcommand}";
           };
 
-        mkRubyShell =
-          name: ruby:
-          pkgs.mkShell {
-            packages = [
-              ruby
-              pkgs.bundix
-              helper
-            ];
+          mkHelperApp =
+            subcommand:
+            let
+              script = pkgs.writeShellScriptBin "gemset-${subcommand}" ''
+                exec ${helper}/bin/gemset ${subcommand} "$@"
+              '';
+            in
+            {
+              type = "app";
+              program = "${script}/bin/gemset-${subcommand}";
+            };
 
-            BUNDLE_GEMFILE = "gemsets/${name}/Gemfile";
-          };
-      in
-      {
-        packages = rubies // {
-          gemset-helper = helper;
-        };
-
-        apps =
-          lib.mapAttrs mkRubyApp rubies
-          // lib.mapAttrs' (name: ruby: lib.nameValuePair "bundle-${name}" (mkBundleApp name ruby)) rubies
-          // lib.optionalAttrs (rubies ? default) {
-            default = mkRubyApp "default" rubies.default;
-            ruby = mkRubyApp "default" rubies.default;
-          }
-          // {
-            gemset-create = mkHelperApp "create";
-            gemset-delete = mkHelperApp "delete";
-            gemset-lock = mkHelperApp "lock";
-            gemset-update = mkHelperApp "update";
+          mkRubyShell =
+            name: ruby:
+            pkgs.mkShell {
+              packages = [
+                ruby
+                pkgs.bundix
+                helper
+              ];
+
+              BUNDLE_GEMFILE = "gemsets/${name}/Gemfile";
+            };
+        in
+        {
+          packages = rubies // {
+            gemset-helper = helper;
           };
 
-        devShells = lib.mapAttrs mkRubyShell rubies // {
-          default = pkgs.mkShell {
-            packages = [
-              pkgs.bundix
-              helper
-            ]
-            ++ builtins.attrValues rubies;
+          apps =
+            lib.mapAttrs mkRubyApp rubies
+            // lib.mapAttrs' (name: ruby: lib.nameValuePair "bundle-${name}" (mkBundleApp name ruby)) rubies
+            // lib.optionalAttrs (rubies ? default) {
+              default = mkRubyApp "default" rubies.default;
+              ruby = mkRubyApp "default" rubies.default;
+            }
+            // {
+              gemset-create = mkHelperApp "create";
+              gemset-delete = mkHelperApp "delete";
+              gemset-lock = mkHelperApp "lock";
+              gemset-update = mkHelperApp "update";
+            };
+
+          devShells = lib.mapAttrs mkRubyShell rubies // {
+            default = pkgs.mkShell {
+              packages = [
+                pkgs.bundix
+                helper
+              ]
+              ++ builtins.attrValues rubies;
+            };
           };
-        };
-      }
-    );
+        }
+      );
+    in
+    {
+      packages = forEachSystem (system: perSystem.${system}.packages);
+      apps = forEachSystem (system: perSystem.${system}.apps);
+      devShells = forEachSystem (system: perSystem.${system}.devShells);
+    };
 }