diff --git a/.rubocop.yml b/.rubocop.yml
index c2504a32..08ae1f2b 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -4,7 +4,7 @@ inherit_gem:
   rubocop-jekyll: .rubocop.yml
 
 AllCops:
-  TargetRubyVersion: 2.3
+  TargetRubyVersion: 2.4
   Include:
     - lib/**/*.rb
 
diff --git a/.travis.yml b/.travis.yml
index cfe5110b..59609160 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,8 +2,8 @@ language: ruby
 cache: bundler
 sudo: false
 rvm:
-- 2.5
-- 2.3
+- 2.6
+- 2.4
 env:
   global:
   - NOKOGIRI_USE_SYSTEM_LIBRARIES=true
diff --git a/Gemfile b/Gemfile
index 9a5d6595..e5cf9dca 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,6 +3,4 @@
 source "https://rubygems.org"
 gemspec
 
-if ENV["JEKYLL_VERSION"]
-  gem "jekyll", "~> #{ENV["JEKYLL_VERSION"]}"
-end
+gem "jekyll", "~> #{ENV["JEKYLL_VERSION"]}" if ENV["JEKYLL_VERSION"]
diff --git a/jekyll-feed.gemspec b/jekyll-feed.gemspec
index 593f9195..e62f86ba 100644
--- a/jekyll-feed.gemspec
+++ b/jekyll-feed.gemspec
@@ -21,10 +21,10 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = ">= 2.3.0"
 
   spec.add_dependency "jekyll", "~> 3.3"
-  spec.add_development_dependency "bundler", "~> 1.15"
+  spec.add_development_dependency "bundler"
   spec.add_development_dependency "nokogiri", "~> 1.6"
   spec.add_development_dependency "rake", "~> 12.0"
   spec.add_development_dependency "rspec", "~> 3.0"
-  spec.add_development_dependency "rubocop-jekyll", "~> 0.4"
+  spec.add_development_dependency "rubocop-jekyll", "~> 0.5"
   spec.add_development_dependency "typhoeus", ">= 0.7", "< 2.0"
 end