diff --git a/digest-keccak.gemspec b/digest-keccak.gemspec
index e4847ea..e73191d 100644
--- a/digest-keccak.gemspec
+++ b/digest-keccak.gemspec
@@ -13,7 +13,7 @@ Gem::Specification.new do |spec|
   spec.summary  = 'The Keccak cryptographic hash function.'
   spec.platform = Gem::Platform::RUBY
 
-  spec.required_ruby_version = '~> 2.2'
+  spec.required_ruby_version = '>= 2.2', '< 4'
 
   spec.authors = ['Alex Kotov', 'Hongli Lai (Phusion)', 'Keccak authors']
   spec.email   = %w[kotovalexarian@gmail.com]