diff --git a/lib/uri/uri.gemspec b/lib/uri/uri.gemspec
index c4a16f47eb..584a4faa11 100644
--- a/lib/uri/uri.gemspec
+++ b/lib/uri/uri.gemspec
@@ -15,6 +15,8 @@ Gem::Specification.new do |spec|
   spec.homepage      = "https://github.com/ruby/uri"
   spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
+  spec.required_ruby_version = '>= 2.4'
+
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage