diff --git a/.rubocop.yml b/.rubocop.yml
index 3abbf6b..41bea7f 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,5 +1,5 @@
 AllCops:
-  TargetRubyVersion: 2.4
+  TargetRubyVersion: 2.5
   NewCops: enable
   Exclude:
     - "*.gemspec"
diff --git a/jekyll-toc.gemspec b/jekyll-toc.gemspec
index abd1cf3..c73f97f 100644
--- a/jekyll-toc.gemspec
+++ b/jekyll-toc.gemspec
@@ -17,8 +17,8 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec)/})
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = '>= 2.4'
+  spec.required_ruby_version = '>= 2.5'
 
   spec.add_dependency 'jekyll', '>= 3.9'
-  spec.add_dependency 'nokogiri', '~> 1.10'
+  spec.add_dependency 'nokogiri', '~> 1.11'
 end