diff --git a/.rubocop.yml b/.rubocop.yml
index cf91fe2..4631b4a 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,5 +1,28 @@
 AllCops:
+  TargetRubyVersion: 2.2
   DisabledByDefault: true
+  Exclude:
+    - "examples/instrumentation.rb"
+
+Bundler:
+  Enabled: true
+
+Gemspec:
+  Enabled: true
 
 Layout:
   Enabled: true
+
+Performance:
+  Enabled: true
+
+Security:
+  Enabled: true
+
+Lint:
+  Enabled: true
+
+# TODO
+# Remove cop disabling and fix offenses
+Lint/HandleExceptions:
+  Enabled: false
diff --git a/Appraisals b/Appraisals
index 839a9f4..f0495db 100644
--- a/Appraisals
+++ b/Appraisals
@@ -7,18 +7,18 @@ appraise "rack_1_6" do
 end
 
 appraise 'rails_5-2' do
-  gem 'activesupport', '~> 5.2.0'
   gem 'actionpack', '~> 5.2.0'
+  gem 'activesupport', '~> 5.2.0'
 end
 
 appraise 'rails_5-1' do
-  gem 'activesupport', '~> 5.1.0'
   gem 'actionpack', '~> 5.1.0'
+  gem 'activesupport', '~> 5.1.0'
 end
 
 appraise 'rails_4-2' do
-  gem 'activesupport', '~> 4.2.0'
   gem 'actionpack', '~> 4.2.0'
+  gem 'activesupport', '~> 4.2.0'
 end
 
 appraise 'dalli2' do
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index f6f248f..d664561 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -20,7 +20,7 @@ Any of the following is greatly appreciated:
 As an effort to keep the codebase consistent, we encourage the use of [Rubocop](https://github.com/bbatsov/rubocop).
 This tool helps us abstract most of the decisions we have to make when coding.
 
-To check your code, simply type `rubocop` in the shell. The resulting output are all the offenses currently present in the code.
+To check your code, simply type `bundle exec rubocop` in the shell. The resulting output are all the offenses currently present in the code.
 
 It is highly recommended that you integrate a linter with your editor.
 This way you receive real time feedback about your code. Most editors have some kind of plugin for that.
diff --git a/gemfiles/rails_4_2.gemfile b/gemfiles/rails_4_2.gemfile
index 7a03e76..3937ece 100644
--- a/gemfiles/rails_4_2.gemfile
+++ b/gemfiles/rails_4_2.gemfile
@@ -2,7 +2,7 @@
 
 source "https://rubygems.org"
 
-gem "activesupport", "~> 4.2.0"
 gem "actionpack", "~> 4.2.0"
+gem "activesupport", "~> 4.2.0"
 
 gemspec path: "../"
diff --git a/gemfiles/rails_5_1.gemfile b/gemfiles/rails_5_1.gemfile
index 98a6051..d05d8e4 100644
--- a/gemfiles/rails_5_1.gemfile
+++ b/gemfiles/rails_5_1.gemfile
@@ -2,7 +2,7 @@
 
 source "https://rubygems.org"
 
-gem "activesupport", "~> 5.1.0"
 gem "actionpack", "~> 5.1.0"
+gem "activesupport", "~> 5.1.0"
 
 gemspec path: "../"
diff --git a/gemfiles/rails_5_2.gemfile b/gemfiles/rails_5_2.gemfile
index 41b8b1b..d12b8c6 100644
--- a/gemfiles/rails_5_2.gemfile
+++ b/gemfiles/rails_5_2.gemfile
@@ -2,7 +2,7 @@
 
 source "https://rubygems.org"
 
-gem "activesupport", "~> 5.2.0"
 gem "actionpack", "~> 5.2.0"
+gem "activesupport", "~> 5.2.0"
 
 gemspec path: "../"
diff --git a/lib/rack/attack.rb b/lib/rack/attack.rb
index ad5e1eb..c7596ef 100644
--- a/lib/rack/attack.rb
+++ b/lib/rack/attack.rb
@@ -101,7 +101,7 @@ class Rack::Attack
     end
 
     def throttled?(req)
-      throttles.any? do |name, throttle|
+      throttles.any? do |_name, throttle|
         throttle[req]
       end
     end
@@ -149,7 +149,7 @@ class Rack::Attack
 
   # Set defaults
   @notifier             = ActiveSupport::Notifications if defined?(ActiveSupport::Notifications)
-  @blocklisted_response = lambda { |env| [403, { 'Content-Type' => 'text/plain' }, ["Forbidden\n"]] }
+  @blocklisted_response = lambda { |_env| [403, { 'Content-Type' => 'text/plain' }, ["Forbidden\n"]] }
   @throttled_response   = lambda { |env|
     retry_after = (env['rack.attack.match_data'] || {})[:period]
     [429, { 'Content-Type' => 'text/plain', 'Retry-After' => retry_after.to_s }, ["Retry later\n"]]
diff --git a/lib/rack/attack/store_proxy.rb b/lib/rack/attack/store_proxy.rb
index d8edddb..d83cab9 100644
--- a/lib/rack/attack/store_proxy.rb
+++ b/lib/rack/attack/store_proxy.rb
@@ -12,8 +12,6 @@ module Rack
         klass ? klass.new(client) : client
       end
 
-      private
-
       def self.unwrap_active_support_stores(store)
         # ActiveSupport::Cache::RedisStore doesn't expose any way to set an expiry,
         # so use the raw Redis::Store instead.
diff --git a/lib/rack/attack/store_proxy/mem_cache_proxy.rb b/lib/rack/attack/store_proxy/mem_cache_proxy.rb
index bc23942..4675789 100644
--- a/lib/rack/attack/store_proxy/mem_cache_proxy.rb
+++ b/lib/rack/attack/store_proxy/mem_cache_proxy.rb
@@ -23,12 +23,12 @@ module Rack
         rescue MemCache::MemCacheError
         end
 
-        def increment(key, amount, options = {})
+        def increment(key, amount, _options = {})
           incr(key, amount)
         rescue MemCache::MemCacheError
         end
 
-        def delete(key, options = {})
+        def delete(key, _options = {})
           with do |client|
             client.delete(key)
           end
diff --git a/lib/rack/attack/store_proxy/redis_store_proxy.rb b/lib/rack/attack/store_proxy/redis_store_proxy.rb
index 9833c26..1741b99 100644
--- a/lib/rack/attack/store_proxy/redis_store_proxy.rb
+++ b/lib/rack/attack/store_proxy/redis_store_proxy.rb
@@ -45,7 +45,7 @@ module Rack
         rescue Redis::BaseError
         end
 
-        def delete(key, options = {})
+        def delete(key, _options = {})
           del(key)
         rescue Redis::BaseError
         end
diff --git a/rack-attack.gemspec b/rack-attack.gemspec
index 6803d0a..f63c35c 100644
--- a/rack-attack.gemspec
+++ b/rack-attack.gemspec
@@ -21,24 +21,26 @@ Gem::Specification.new do |s|
   s.summary = %q{Block & throttle abusive requests}
   s.test_files = Dir.glob("spec/**/*")
 
-  s.required_ruby_version = '>= 2.0.0'
+  s.required_ruby_version = '>= 2.2'
 
   s.add_dependency 'rack'
 
+  s.add_development_dependency 'actionpack', '>= 3.0.0'
+  s.add_development_dependency 'activesupport', '>= 3.0.0'
+  s.add_development_dependency 'appraisal'
+  s.add_development_dependency 'connection_pool'
+  s.add_development_dependency 'dalli'
+  s.add_development_dependency 'guard-minitest'
+  s.add_development_dependency 'memcache-client'
   s.add_development_dependency 'minitest'
   s.add_development_dependency "minitest-stub-const"
+  s.add_development_dependency 'pry'
   s.add_development_dependency 'rack-test'
   s.add_development_dependency 'rake'
-  s.add_development_dependency 'appraisal'
-  s.add_development_dependency 'activesupport', '>= 3.0.0'
-  s.add_development_dependency 'actionpack', '>= 3.0.0'
   s.add_development_dependency 'redis-activesupport'
-  s.add_development_dependency 'dalli'
-  s.add_development_dependency 'connection_pool'
-  s.add_development_dependency 'memcache-client'
+  s.add_development_dependency "rubocop", "0.55.0"
   s.add_development_dependency "timecop"
-  s.add_development_dependency 'pry'
-  s.add_development_dependency 'guard-minitest'
+
   # Need to explicitly depend on guard because guard-minitest doesn't declare
   # the dependency intentionally
   #
diff --git a/spec/acceptance/cache_store_config_for_allow2ban_spec.rb b/spec/acceptance/cache_store_config_for_allow2ban_spec.rb
index aa7208e..4b6cb11 100644
--- a/spec/acceptance/cache_store_config_for_allow2ban_spec.rb
+++ b/spec/acceptance/cache_store_config_for_allow2ban_spec.rb
@@ -81,11 +81,11 @@ describe "Cache store config when using allow2ban" do
         @backend[key]
       end
 
-      def write(key, value, options = {})
+      def write(key, value, _options = {})
         @backend[key] = value
       end
 
-      def increment(key, count, options = {})
+      def increment(key, _count, _options = {})
         @backend[key] ||= 0
         @backend[key] += 1
       end
diff --git a/spec/acceptance/cache_store_config_for_fail2ban_spec.rb b/spec/acceptance/cache_store_config_for_fail2ban_spec.rb
index 53b43e5..4f978a1 100644
--- a/spec/acceptance/cache_store_config_for_fail2ban_spec.rb
+++ b/spec/acceptance/cache_store_config_for_fail2ban_spec.rb
@@ -81,11 +81,11 @@ describe "Cache store config when using fail2ban" do
         @backend[key]
       end
 
-      def write(key, value, options = {})
+      def write(key, value, _options = {})
         @backend[key] = value
       end
 
-      def increment(key, count, options = {})
+      def increment(key, _count, _options = {})
         @backend[key] ||= 0
         @backend[key] += 1
       end
diff --git a/spec/acceptance/cache_store_config_for_throttle_spec.rb b/spec/acceptance/cache_store_config_for_throttle_spec.rb
index 9df9a6c..524048b 100644
--- a/spec/acceptance/cache_store_config_for_throttle_spec.rb
+++ b/spec/acceptance/cache_store_config_for_throttle_spec.rb
@@ -29,7 +29,7 @@ describe "Cache store config when throttling without Rails" do
         @counts = {}
       end
 
-      def increment(key, count, options)
+      def increment(key, _count, _options)
         @counts[key] ||= 0
         @counts[key] += 1
       end
diff --git a/spec/acceptance/customizing_blocked_response_spec.rb b/spec/acceptance/customizing_blocked_response_spec.rb
index 190f5c0..cf297b0 100644
--- a/spec/acceptance/customizing_blocked_response_spec.rb
+++ b/spec/acceptance/customizing_blocked_response_spec.rb
@@ -12,7 +12,7 @@ describe "Customizing block responses" do
 
     assert_equal 403, last_response.status
 
-    Rack::Attack.blocklisted_response = lambda do |env|
+    Rack::Attack.blocklisted_response = lambda do |_env|
       [503, {}, ["Blocked"]]
     end
 
diff --git a/spec/acceptance/customizing_throttled_response_spec.rb b/spec/acceptance/customizing_throttled_response_spec.rb
index 5f657aa..61acc01 100644
--- a/spec/acceptance/customizing_throttled_response_spec.rb
+++ b/spec/acceptance/customizing_throttled_response_spec.rb
@@ -18,7 +18,7 @@ describe "Customizing throttled response" do
 
     assert_equal 429, last_response.status
 
-    Rack::Attack.throttled_response = lambda do |env|
+    Rack::Attack.throttled_response = lambda do |_env|
       [503, {}, ["Throttled"]]
     end
 
diff --git a/spec/rack_attack_throttle_spec.rb b/spec/rack_attack_throttle_spec.rb
index 8a0df19..0361c7c 100644
--- a/spec/rack_attack_throttle_spec.rb
+++ b/spec/rack_attack_throttle_spec.rb
@@ -51,7 +51,7 @@ describe 'Rack::Attack.throttle with limit as proc' do
   before do
     @period = 60 # Use a long period; failures due to cache key rotation less likely
     Rack::Attack.cache.store = ActiveSupport::Cache::MemoryStore.new
-    Rack::Attack.throttle('ip/sec', :limit => lambda { |req| 1 }, :period => @period) { |req| req.ip }
+    Rack::Attack.throttle('ip/sec', :limit => lambda { |_req| 1 }, :period => @period) { |req| req.ip }
   end
 
   it_allows_ok_requests
@@ -75,7 +75,7 @@ describe 'Rack::Attack.throttle with period as proc' do
   before do
     @period = 60 # Use a long period; failures due to cache key rotation less likely
     Rack::Attack.cache.store = ActiveSupport::Cache::MemoryStore.new
-    Rack::Attack.throttle('ip/sec', :limit => lambda { |req| 1 }, :period => lambda { |req| @period }) { |req| req.ip }
+    Rack::Attack.throttle('ip/sec', :limit => lambda { |_req| 1 }, :period => lambda { |_req| @period }) { |req| req.ip }
   end
 
   it_allows_ok_requests
diff --git a/spec/rack_attack_track_spec.rb b/spec/rack_attack_track_spec.rb
index 8e0f9c6..24a408f 100644
--- a/spec/rack_attack_track_spec.rb
+++ b/spec/rack_attack_track_spec.rb
@@ -16,7 +16,7 @@ describe 'Rack::Attack.track' do
   end
 
   before do
-    Rack::Attack.track("everything") { |req| true }
+    Rack::Attack.track("everything") { |_req| true }
   end
 
   it_allows_ok_requests
@@ -33,7 +33,7 @@ describe 'Rack::Attack.track' do
       # A second track
       Rack::Attack.track("homepage") { |req| req.path == "/" }
 
-      ActiveSupport::Notifications.subscribe("rack.attack") do |*args|
+      ActiveSupport::Notifications.subscribe("rack.attack") do |*_args|
         Counter.incr
       end
 
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 7d62673..8f8a71d 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -42,7 +42,7 @@ class MiniTest::Spec
       use Rack::Attack
       use Rack::Lint
 
-      run lambda { |env| [200, {}, ['Hello World']] }
+      run lambda { |_env| [200, {}, ['Hello World']] }
     }.to_app
   end