diff --git a/.github/workflows/test-suite.yml b/.github/workflows/test-suite.yml
index a983437..27fd60f 100644
--- a/.github/workflows/test-suite.yml
+++ b/.github/workflows/test-suite.yml
@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [3.2, 3.1, '3.0']
+        ruby: [3.2, 3.1, '3.0', 2.7, 2.6, 2.5, 2.4]
 
     steps:
     - uses: actions/checkout@v2
diff --git a/writeexcel.gemspec b/writeexcel.gemspec
index 9595f30..19bec4b 100644
--- a/writeexcel.gemspec
+++ b/writeexcel.gemspec
@@ -17,7 +17,7 @@ Gem::Specification.new do |gem|
   gem.executables   = gem.files.grep(%r{^bin/}).map{ |f| File.basename(f) }
   gem.test_files    = gem.files.grep(%r{^(test|spec|features)/})
   gem.require_paths = ["lib"]
-  gem.required_ruby_version = '>= 3.0.0'
+  gem.required_ruby_version = '>= 2.4.0'
   gem.add_development_dependency 'minitest'
   gem.add_development_dependency 'rake'
   gem.extra_rdoc_files = [