diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 396265b..ee000f6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,7 +8,7 @@ jobs:
 
     strategy:
       matrix:
-        ruby: ['3.2', '3.1', '3.0']
+        ruby: ['3.3', '3.2', '3.1', '3.0']
         frozen_string_literal: ['yes', 'no']
 
     env:
diff --git a/rggen-core.gemspec b/rggen-core.gemspec
index a9b9621..2ddf5f7 100644
--- a/rggen-core.gemspec
+++ b/rggen-core.gemspec
@@ -26,7 +26,7 @@ Gem::Specification.new do |spec|
   spec.executables = spec.files.grep(/^exe\//) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = '>= 3.0'
+  spec.required_ruby_version = Gem::Requirement.new('>= 3.0.0')
 
   spec.add_runtime_dependency 'docile', '>= 1.1.5', '!= 1.3.3'
   spec.add_runtime_dependency 'erubi', '>= 1.7'