diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index ceceac4..299e97c 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -14,7 +14,7 @@ jobs:
       matrix:
         activesupport: ['7.1', '7.2', '8.0', '8.1']
         json_schemer: ['2.1', '2.2', '2.3', '2.4', '2.5']
-        ruby: ['3.2', '3.3', '3.4']
+        ruby: ['3.2', '3.3', '3.4', '4.0']
     env:
       ACTIVESUPPORT: '${{ matrix.activesupport }}'
       COVERAGE: 'true'
@@ -37,7 +37,7 @@ jobs:
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 3.4
+        ruby-version: 4.0
         bundler-cache: true
         cache-version: '7.1'
     - name: Rubocop
diff --git a/.ruby-version b/.ruby-version
index 2aa5131..fcdb2e1 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.4.7
+4.0.0
diff --git a/openapi_contracts.gemspec b/openapi_contracts.gemspec
index 53da130..9c113f1 100644
--- a/openapi_contracts.gemspec
+++ b/openapi_contracts.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.homepage    = 'https://github.com/mkon/openapi_contracts'
   s.summary     = 'Openapi schemas as API contracts'
   s.license     = 'MIT'
-  s.required_ruby_version = '>= 3.2', '< 3.5'
+  s.required_ruby_version = '>= 3.2', '< 4.1'
 
   s.files = Dir['lib/**/*', 'README.md']