diff --git a/.rubocop.yml b/.rubocop.yml
index 8f961cf5..f483e1dd 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,6 +1,6 @@
 ---
 AllCops:
-  TargetRubyVersion: 2.0
+  TargetRubyVersion: 2.1
   Include:
     - lib/**/*.rb
   Exclude:
@@ -117,8 +117,6 @@ Style/Documentation:
     - !ruby/regexp /features\/.*.rb$/
 Style/DoubleNegation:
   Enabled: false
-Style/Encoding:
-  EnforcedStyle: when_needed
 Style/GuardClause:
   Enabled: false
 Style/HashSyntax:
diff --git a/Gemfile b/Gemfile
index 8ff6d132..92f6f45e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -30,7 +30,7 @@ group :test do
   gem "nokogiri", RUBY_VERSION >= "2.2" ? "~> 1.7" : "~> 1.7.0"
   gem "rspec"
   gem "rspec-mocks"
-  gem "rubocop", "~> 0.50.0"
+  gem "rubocop", "~> 0.51.0"
   gem "test-dependency-theme", :path => File.expand_path("test/fixtures/test-dependency-theme", __dir__)
   gem "test-theme", :path => File.expand_path("test/fixtures/test-theme", __dir__)
 
diff --git a/features/step_definitions.rb b/features/step_definitions.rb
index 29900491..c69cc089 100644
--- a/features/step_definitions.rb
+++ b/features/step_definitions.rb
@@ -156,7 +156,7 @@ end
 When(%r!^I run jekyll(.*)$!) do |args|
   run_jekyll(args)
   if args.include?("--verbose") || ENV["DEBUG"]
-    $stderr.puts "\n#{jekyll_run_output}\n"
+    warn "\n#{jekyll_run_output}\n"
   end
 end
 
@@ -165,7 +165,7 @@ end
 When(%r!^I run bundle(.*)$!) do |args|
   run_bundle(args)
   if args.include?("--verbose") || ENV["DEBUG"]
-    $stderr.puts "\n#{jekyll_run_output}\n"
+    warn "\n#{jekyll_run_output}\n"
   end
 end
 
@@ -174,7 +174,7 @@ end
 When(%r!^I run gem(.*)$!) do |args|
   run_rubygem(args)
   if args.include?("--verbose") || ENV["DEBUG"]
-    $stderr.puts "\n#{jekyll_run_output}\n"
+    warn "\n#{jekyll_run_output}\n"
   end
 end
 
diff --git a/lib/jekyll/commands/build.rb b/lib/jekyll/commands/build.rb
index 1bd176b8..96a48cdf 100644
--- a/lib/jekyll/commands/build.rb
+++ b/lib/jekyll/commands/build.rb
@@ -96,7 +96,7 @@ module Jekyll
             )
           end
         end
-      end # end of class << self
+      end
     end
   end
 end
diff --git a/lib/jekyll/configuration.rb b/lib/jekyll/configuration.rb
index 5c502d68..575dca65 100644
--- a/lib/jekyll/configuration.rb
+++ b/lib/jekyll/configuration.rb
@@ -207,7 +207,7 @@ module Jekyll
       rescue ArgumentError => err
         Jekyll.logger.warn "WARNING:", "Error reading configuration. " \
                      "Using defaults (and options)."
-        $stderr.puts err
+        warn err
       end
 
       configuration.fix_common_issues.backwards_compatibilize.add_default_collections
diff --git a/lib/jekyll/converters/markdown/redcarpet_parser.rb b/lib/jekyll/converters/markdown/redcarpet_parser.rb
index 35c6e5fe..7a8c6ec5 100644
--- a/lib/jekyll/converters/markdown/redcarpet_parser.rb
+++ b/lib/jekyll/converters/markdown/redcarpet_parser.rb
@@ -47,7 +47,7 @@ class Jekyll::Converters::Markdown::RedcarpetParser
   end
 
   module WithRouge
-    def block_code(code, lang)
+    def block_code(_code, lang)
       code = "<pre>#{super}</pre>"
 
       "<div class=\"highlight\">#{add_code_tags(code, lang)}</div>"
diff --git a/test/test_filters.rb b/test/test_filters.rb
index 0499b73c..588a1f30 100644
--- a/test/test_filters.rb
+++ b/test/test_filters.rb
@@ -1,4 +1,3 @@
-# coding: utf-8
 # frozen_string_literal: true
 
 require "helper"
diff --git a/test/test_kramdown.rb b/test/test_kramdown.rb
index e1bf15a4..2a12a090 100644
--- a/test/test_kramdown.rb
+++ b/test/test_kramdown.rb
@@ -1,4 +1,3 @@
-# encoding: UTF-8
 # frozen_string_literal: true
 
 require "helper"
diff --git a/test/test_tags.rb b/test/test_tags.rb
index 8a7ed7d0..43d83464 100644
--- a/test/test_tags.rb
+++ b/test/test_tags.rb
@@ -1,4 +1,3 @@
-# coding: utf-8
 # frozen_string_literal: true
 
 require "helper"
diff --git a/test/test_utils.rb b/test/test_utils.rb
index 7d728a89..01c1d98c 100644
--- a/test/test_utils.rb
+++ b/test/test_utils.rb
@@ -1,4 +1,3 @@
-# encoding: utf-8
 # frozen_string_literal: true
 
 require "helper"