diff --git a/.rubocop.yml b/.rubocop.yml
index 08ae1f2b..c8639713 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,27 +1,38 @@
+inherit_from: .rubocop_todo.yml
+
 require: rubocop-jekyll
 
 inherit_gem:
   rubocop-jekyll: .rubocop.yml
 
 AllCops:
-  TargetRubyVersion: 2.4
-  Include:
-    - lib/**/*.rb
-
+  TargetRubyVersion: 2.5
+  SuggestExtensions: false
   Exclude:
-    - .gitignore
-    - .rspec
-    - .rubocop.yml
-    - .travis.yml
+    - vendor/**/*
 
-    - Gemfile.lock
-    - History.markdown
-    - LICENSE.txt
-    - README.md
+Layout/LineEndStringConcatenationIndentation:
+  Enabled: true
 
-    - script/**/*
-    - vendor/**/*
+Lint/EmptyInPattern:
+  Enabled: false
 
+Naming/InclusiveLanguage:
+  Enabled: false
 Naming/MemoizedInstanceVariableName:
   Exclude:
     - lib/jekyll-feed/page-without-a-file.rb
+
+Performance/MapCompact:
+  Enabled: true
+Performance/RedundantEqualityComparisonBlock:
+  Enabled: true
+Performance/RedundantSplitRegexpArgument:
+  Enabled: true
+
+Style/InPatternThen:
+  Enabled: false
+Style/MultilineInPatternThen:
+  Enabled: false
+Style/QuotedSymbols:
+  Enabled: true
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
new file mode 100644
index 00000000..500786af
--- /dev/null
+++ b/.rubocop_todo.yml
@@ -0,0 +1,65 @@
+# This configuration was generated by
+# `rubocop --auto-gen-config`
+# on 2021-09-17 11:44:51 UTC using RuboCop version 1.18.4.
+# The point is for the user to remove these configuration records
+# one by one as the offenses are removed from the code base.
+# Note that changes in the inspected code, or installation of new
+# versions of RuboCop, may require this file to be generated again.
+
+# Offense count: 1
+# Cop supports --auto-correct.
+Layout/EmptyLines:
+  Exclude:
+    - 'spec/jekyll-feed_spec.rb'
+
+# Offense count: 15
+# Cop supports --auto-correct.
+# Configuration parameters: AutoCorrect, AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, IgnoredPatterns.
+# URISchemes: http, https
+Layout/LineLength:
+  Max: 144
+
+# Offense count: 3
+# Configuration parameters: AllowedMethods.
+# AllowedMethods: enums
+Lint/ConstantDefinitionInBlock:
+  Exclude:
+    - 'spec/jekyll-feed_spec.rb'
+    - 'spec/spec_helper.rb'
+
+# Offense count: 3
+# Cop supports --auto-correct.
+Performance/RegexpMatch:
+  Exclude:
+    - 'spec/jekyll-feed_spec.rb'
+
+# Offense count: 2
+# Cop supports --auto-correct.
+# Configuration parameters: AutoCorrect.
+Performance/StringInclude:
+  Exclude:
+    - 'spec/jekyll-feed_spec.rb'
+
+# Offense count: 2
+# Cop supports --auto-correct.
+# Configuration parameters: EnforcedStyle, UseHashRocketsWithSymbolValues, PreferHashRocketsForNonAlnumEndingSymbols.
+# SupportedStyles: ruby19, hash_rockets, no_mixed_keys, ruby19_no_mixed_keys
+Style/HashSyntax:
+  Exclude:
+    - 'spec/jekyll-feed_spec.rb'
+
+# Offense count: 7
+# Cop supports --auto-correct.
+# Configuration parameters: EnforcedStyle, ConsistentQuotesInMultiline.
+# SupportedStyles: single_quotes, double_quotes
+Style/StringLiterals:
+  Exclude:
+    - 'spec/jekyll-feed_spec.rb'
+
+# Offense count: 5
+# Cop supports --auto-correct.
+# Configuration parameters: EnforcedStyleForMultiline.
+# SupportedStylesForMultiline: comma, consistent_comma, no_comma
+Style/TrailingCommaInHashLiteral:
+  Exclude:
+    - 'spec/jekyll-feed_spec.rb'
diff --git a/Gemfile b/Gemfile
index e1c7ddf3..1a27d6d2 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,9 +3,9 @@
 source "https://rubygems.org"
 gemspec
 
-gem "rss" if RUBY_VERSION >= "3.0.0"
 gem "jekyll", ENV["JEKYLL_VERSION"] if ENV["JEKYLL_VERSION"]
 gem "kramdown-parser-gfm" if ENV["JEKYLL_VERSION"] == "~> 3.9"
+gem "rss" if RUBY_VERSION >= "3.0.0"
 
 install_if -> { Gem.win_platform? } do
   gem "tzinfo", "~> 1.2"
diff --git a/appveyor.yml b/appveyor.yml
index e6716814..d9776686 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -11,7 +11,6 @@ environment:
     - RUBY_FOLDER_VER: "26"
       JEKYLL_VERSION : ">= 4.0.0.pre.alpha1"
     - RUBY_FOLDER_VER: "26"
-    - RUBY_FOLDER_VER: "24"
 
 install:
   - SET PATH=C:\Ruby%RUBY_FOLDER_VER%-x64\bin;%PATH%
diff --git a/jekyll-feed.gemspec b/jekyll-feed.gemspec
index f96b9a32..cf1508e8 100644
--- a/jekyll-feed.gemspec
+++ b/jekyll-feed.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.test_files       = spec.files.grep(%r!^spec/!)
   spec.require_paths    = ["lib"]
 
-  spec.required_ruby_version = ">= 2.4.0"
+  spec.required_ruby_version = ">= 2.5.0"
 
   spec.add_dependency "jekyll", ">= 3.7", "< 5.0"
 
@@ -24,6 +24,6 @@ Gem::Specification.new do |spec|
   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", "~> 0.5"
+  spec.add_development_dependency "rubocop-jekyll", "~> 0.12.0"
   spec.add_development_dependency "typhoeus", ">= 0.7", "< 2.0"
 end
diff --git a/lib/jekyll-feed/generator.rb b/lib/jekyll-feed/generator.rb
index ade634ae..3f285bef 100644
--- a/lib/jekyll-feed/generator.rb
+++ b/lib/jekyll-feed/generator.rb
@@ -54,9 +54,10 @@ def feed_path(collection: "posts", category: nil)
     def collections
       return @collections if defined?(@collections)
 
-      @collections = if config["collections"].is_a?(Array)
+      @collections = case config["collections"]
+                     when Array
                        config["collections"].map { |c| [c, {}] }.to_h
-                     elsif config["collections"].is_a?(Hash)
+                     when Hash
                        config["collections"]
                      else
                        {}
diff --git a/script/fmt b/script/fmt
index c5351ecf..913591ad 100755
--- a/script/fmt
+++ b/script/fmt
@@ -1,7 +1,7 @@
 #!/bin/bash
 set -e
 
-echo "Rubocop $(bundle exec rubocop --version)"
+echo "RuboCop $(bundle exec rubocop --version)"
 bundle exec rubocop -D -E $@
 success=$?
 if ((success != 0)); then