diff --git a/lib/rb/thrift.gemspec b/lib/rb/thrift.gemspec
index 7e1bb33..d763bad 100644
--- a/lib/rb/thrift.gemspec
+++ b/lib/rb/thrift.gemspec
@@ -12,6 +12,8 @@
   s.license     = 'Apache-2.0'
   s.extensions  = ['ext/extconf.rb']
 
+  s.required_ruby_version = '>= 2.4.0'
+
   s.rdoc_options  = %w[--line-numbers --inline-source --title Thrift --main README]
 
   dir = File.expand_path(File.dirname(__FILE__))