diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index a3506a8..926d1d7 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -29,6 +29,7 @@ jobs:
           - "3.2"
           - "3.3"
           - "3.4"
+          - "4.0"
         allow_failures:
           - false
         include:
diff --git a/contracts.gemspec b/contracts.gemspec
index 320e8d7..f05b290 100644
--- a/contracts.gemspec
+++ b/contracts.gemspec
@@ -12,5 +12,5 @@ Gem::Specification.new do |s|
   s.files       = `git ls-files`.split("\n")
   s.homepage    = "https://github.com/egonSchiele/contracts.ruby"
   s.license     = "BSD-2-Clause"
-  s.required_ruby_version = [">= 3.0", "< 4"]
+  s.required_ruby_version = [">= 3.0", "< 5"]
 end