relaton_iso_bib.gemspec in relaton-iso-bib-0.2.0 vs relaton_iso_bib.gemspec in relaton-iso-bib-0.2.1

@@ -21,9 +21,10 @@
     `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
   end
   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(">= 2.4.0")
 
   spec.add_development_dependency "bundler", "~> 2.0"
   spec.add_development_dependency "pry-byebug"
   spec.add_development_dependency "rake", "~> 10.0"
   spec.add_development_dependency "rspec", "~> 3.0"