diff --git a/.rubocop.yml b/.rubocop.yml
index 973f94e5..9377cc0e 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -12,7 +12,7 @@ AllCops:
     - "vendor/**/*"
     - "db/**/*"
     - "node_modules/**/*"
-  TargetRubyVersion: 3.4
+  TargetRubyVersion: 4.0
   NewCops: enable
 
 Layout/FirstArrayElementIndentation:
diff --git a/.ruby-version b/.ruby-version
index 47b322c9..5186d070 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.4.1
+4.0
diff --git a/Gemfile b/Gemfile
index 30d043b1..c072dfdf 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,7 +1,7 @@
 source 'https://rubygems.org'
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
-ruby '~> 3.4.1'
+ruby '~> 4.0.0'
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 8.1'
diff --git a/Gemfile.lock b/Gemfile.lock
index 9d58fa83..60744515 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -458,7 +458,7 @@ CHECKSUMS
   zeitwerk (2.7.4) sha256=2bef90f356bdafe9a6c2bd32bcd804f83a4f9b8bc27f3600fff051eb3edcec8b
 
 RUBY VERSION
-   ruby 3.4.1p0
+  ruby 4.0.0
 
 BUNDLED WITH
-   2.6.9
+  4.0.3
diff --git a/flake.nix b/flake.nix
index 21a3e497..8f185923 100644
--- a/flake.nix
+++ b/flake.nix
@@ -24,7 +24,7 @@
             (self: super: { inherit bundix; })
           ];
         };
-        ruby = pkgs.ruby_3_4;
+        ruby = pkgs.ruby_4_0;
         gems = pkgs.bundlerEnv {
           name = "accentor-api-env";
           ruby = ruby.override { jemallocSupport = true; };