diff --git a/mutual_recursion.gemspec b/mutual_recursion.gemspec
index b8a0c82..66b9cf6 100644
--- a/mutual_recursion.gemspec
+++ b/mutual_recursion.gemspec
@@ -10,4 +10,5 @@ Gem::Specification.new do |s|
   s.files       = ['lib/mutual_recursion.rb']
   s.homepage    = 'https://gitlab.com/mike-cifelli/mutual_recursion'
   s.license     = 'MIT'
+  s.required_ruby_version = '>= 2.6.0'
 end