diff --git a/.rubocop.yml b/.rubocop.yml
index 7aa4d55..d0581d7 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -14,6 +14,7 @@ Metrics/BlockLength:
     - spec/**/*
 
 Metrics/LineLength:
+  Max: 120
   Exclude:
     - spec/**/*
 
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 633f7be..25a9fae 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -1,67 +1,53 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2016-11-24 18:42:08 +0800 using RuboCop version 0.45.0.
+# on 2017-11-03 11:12:36 +0100 using RuboCop version 0.50.0.
 # 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: 29
+# Offense count: 30
 Metrics/AbcSize:
   Max: 56
 
-# Offense count: 1
-# Configuration parameters: CountComments.
-Metrics/BlockLength:
-  Max: 29
-
 # Offense count: 3
 # Configuration parameters: CountComments.
 Metrics/ClassLength:
   Max: 280
 
-# Offense count: 12
+# Offense count: 10
 Metrics/CyclomaticComplexity:
-  Max: 15
+  Max: 13
 
-# Offense count: 129
-# Configuration parameters: AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives.
-# URISchemes: http, https
-Metrics/LineLength:
-  Max: 120
-
-# Offense count: 35
+# Offense count: 20
 # Configuration parameters: CountComments.
 Metrics/MethodLength:
   Max: 40
 
-# Offense count: 7
+# Offense count: 6
 Metrics/PerceivedComplexity:
-  Max: 16
+  Max: 14
 
 # Offense count: 3
 Style/ClassVars:
   Exclude:
     - 'lib/grape-swagger/doc_methods.rb'
 
-# Offense count: 23
+# Offense count: 20
 Style/Documentation:
   Enabled: false
 
-Style/MixinGrouping:
-  Exclude:
-    - spec/**/*
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Style/MultilineIfModifier:
-  Exclude:
-    - 'lib/grape-swagger/grape/route.rb'
-
-# Offense count: 5
+# Offense count: 4
 # Cop supports --auto-correct.
 # Configuration parameters: EnforcedStyle, SupportedStyles, AllowInnerSlashes.
 # SupportedStyles: slashes, percent_r, mixed
 Style/RegexpLiteral:
   Exclude:
     - 'lib/grape-swagger.rb'
+
+# Offense count: 1
+# Cop supports --auto-correct.
+# Configuration parameters: ConvertCodeThatCanStartToReturnNil.
+Style/SafeNavigation:
+  Exclude:
+    - 'lib/grape-swagger/doc_methods/build_model_definition.rb'
diff --git a/.travis.yml b/.travis.yml
index 21b5979..a287054 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,11 +7,12 @@ before_install:
   - gem install bundler
 
 after_success:
+  - coveralls
   - bundle exec danger
 
 rvm:
-  - 2.4.1
-  - 2.3.4
+  - 2.4.2
+  - 2.3.5
 
 env:
   - MODEL_PARSER=grape-swagger-entity
@@ -27,7 +28,7 @@ matrix:
   fast_finish: true
 
   include:
-    - rvm: 2.2.7
+    - rvm: 2.2.8
       env:
     - rvm: ruby-head
       env:
@@ -37,6 +38,7 @@ matrix:
       env:
 
   allow_failures:
+    - rvm: 2.2.8
     - rvm: ruby-head
     - rvm: jruby-head
     - rvm: rbx-2
diff --git a/Gemfile b/Gemfile
index dbce4a3..d251d44 100644
--- a/Gemfile
+++ b/Gemfile
@@ -25,7 +25,7 @@ group :development, :test do
   gem 'rake'
   gem 'rdoc'
   gem 'rspec', '~> 3.0'
-  gem 'rubocop', '~> 0.49.1'
+  gem 'rubocop', '~>0.51', require: false
 end
 
 group :test do
diff --git a/Rakefile b/Rakefile
index 8d272fa..02c318e 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,4 +1,3 @@
-# encoding: utf-8
 # frozen_string_literal: true
 
 require 'rubygems'
diff --git a/lib/grape-swagger.rb b/lib/grape-swagger.rb
index a35b744..90abb8f 100644
--- a/lib/grape-swagger.rb
+++ b/lib/grape-swagger.rb
@@ -29,9 +29,9 @@ module Grape
         version_for(options)
         options = { target_class: self }.merge(options)
         @target_class = options[:target_class]
-        auth_wrapper = options[:endpoint_auth_wrapper]
+        auth_wrapper = options[:endpoint_auth_wrapper] || Class.new
 
-        if auth_wrapper && auth_wrapper.method_defined?(:before) && !middleware.flatten.include?(auth_wrapper)
+        if auth_wrapper.method_defined?(:before) && !middleware.flatten.include?(auth_wrapper)
           use auth_wrapper
         end
 
@@ -102,7 +102,7 @@ module Grape
 
       def combine_namespace_routes(namespaces)
         # iterate over each single namespace
-        namespaces.each do |name, _|
+        namespaces.each_key do |name, _|
           # get the parent route for the namespace
           parent_route_name = extract_parent_route(name)
           parent_route = @target_class.combined_routes[parent_route_name]
diff --git a/lib/grape-swagger/doc_methods/extensions.rb b/lib/grape-swagger/doc_methods/extensions.rb
index f0e6119..236b02f 100644
--- a/lib/grape-swagger/doc_methods/extensions.rb
+++ b/lib/grape-swagger/doc_methods/extensions.rb
@@ -68,7 +68,7 @@ module GrapeSwagger
         def concatenate(extensions)
           result = {}
 
-          extensions.values.each do |extension|
+          extensions.each_value do |extension|
             extension.each do |key, value|
               result["x-#{key}"] = value
             end
diff --git a/lib/grape-swagger/endpoint.rb b/lib/grape-swagger/endpoint.rb
index 7c01eb5..04138ac 100644
--- a/lib/grape-swagger/endpoint.rb
+++ b/lib/grape-swagger/endpoint.rb
@@ -77,7 +77,7 @@ module Grape
     def path_and_definition_objects(namespace_routes, options)
       @paths = {}
       @definitions = {}
-      namespace_routes.keys.each do |key|
+      namespace_routes.each_key do |key|
         routes = namespace_routes[key]
         path_item(routes, options)
       end
@@ -163,7 +163,7 @@ module Grape
 
     def consumes_object(route, format)
       method = route.request_method.downcase.to_sym
-      if route.settings[:description] && route.settings[:description][:consumes]
+      if route.settings.dig(:description, :consumes)
         format = route.settings[:description][:consumes]
       end
       mime_types = GrapeSwagger::DocMethods::ProducesConsumes.call(format) if %i[post put].include?(method)
@@ -332,7 +332,7 @@ module Grape
       raise GrapeSwagger::Errors::UnregisteredParser, "No parser registered for #{model_name}." unless parser
 
       properties = parser.new(model, self).call
-      unless properties && properties.any?
+      unless properties&.any?
         raise GrapeSwagger::Errors::SwaggerSpec,
               "Empty model #{model_name}, swagger 2.0 doesn't support empty definitions."
       end
diff --git a/spec/issues/403_versions_spec.rb b/spec/issues/403_versions_spec.rb
index ebdde00..80a935f 100644
--- a/spec/issues/403_versions_spec.rb
+++ b/spec/issues/403_versions_spec.rb
@@ -1,4 +1,3 @@
-# encoding: utf-8
 # frozen_string_literal: true
 
 require 'spec_helper'
diff --git a/spec/swagger_v2/api_swagger_v2_mounted_spec.rb b/spec/swagger_v2/api_swagger_v2_mounted_spec.rb
index 34ee43a..6c88573 100644
--- a/spec/swagger_v2/api_swagger_v2_mounted_spec.rb
+++ b/spec/swagger_v2/api_swagger_v2_mounted_spec.rb
@@ -131,7 +131,7 @@ describe 'swagger spec v2.0' do
 
         specify do
           unexpected_paths = mounted_paths - [expected_path]
-          subject.keys.each do |path|
+          subject.each_key do |path|
             unexpected_paths.each do |unexpected_path|
               expect(path).not_to start_with unexpected_path
             end
diff --git a/spec/swagger_v2/guarded_endpoint_spec.rb b/spec/swagger_v2/guarded_endpoint_spec.rb
index 22ef987..f32a0f8 100644
--- a/spec/swagger_v2/guarded_endpoint_spec.rb
+++ b/spec/swagger_v2/guarded_endpoint_spec.rb
@@ -14,14 +14,6 @@ class SampleAuth < Grape::Middleware::Base
       @protected_endpoint || false
     end
 
-    def access_token
-      @_access_token
-    end
-
-    def access_token=(token)
-      @_access_token = token
-    end
-
     def resource_owner
       @resource_owner = true if access_token == '12345'
     end