diff --git a/reline.gemspec b/reline.gemspec
index 5a3d69af3c..d0b12ed36d 100644
--- a/reline.gemspec
+++ b/reline.gemspec
@@ -17,6 +17,8 @@ Gem::Specification.new do |spec|
   spec.files         = Dir['BSDL', 'COPYING', 'README.md', 'lib/**/*']
   spec.require_paths = ['lib']
 
+  spec.required_ruby_version = Gem::Requirement.new('>= 2.5')
+
   spec.add_development_dependency 'bundler'
   spec.add_development_dependency 'rake'
   spec.add_development_dependency 'test-unit'