diff --git a/pubid-iso.gemspec b/pubid-iso.gemspec
index 41aaf69..3b1fdb7 100644
--- a/pubid-iso.gemspec
+++ b/pubid-iso.gemspec
@@ -22,7 +22,7 @@ Gem::Specification.new do |spec|
   spec.bindir        = "exe"
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
-  spec.required_ruby_version = Gem::Requirement.new(">= 3.1.0")
+  spec.required_ruby_version = Gem::Requirement.new(">= 3.3.0")
 
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "rspec", "~> 3.0"