diff --git a/.rubocop.yml b/.rubocop.yml
index 1b62416f74c..965a52c7552 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -657,7 +657,7 @@ Style/Tab:
 Style/TrailingBlankLines:
   Description: 'Checks trailing blank lines and final newline.'
   StyleGuide: 'https://github.com/bbatsov/ruby-style-guide#newline-eof'
-  Enabled: false
+  Enabled: true
 
 Style/TrailingComma:
   Description: 'Checks for trailing comma in parameter lists and literals.'
@@ -909,7 +909,7 @@ Lint/StringConversionInInterpolation:
 
 Lint/UnderscorePrefixedVariableName:
   Description: 'Do not use prefix `_` for a variable that is used.'
-  Enabled: false
+  Enabled: true
 
 Lint/UnusedBlockArgument:
   Description: 'Checks for unused block arguments.'
@@ -966,7 +966,7 @@ Rails/Delegate:
 
 Rails/HasAndBelongsToMany:
   Description: 'Prefer has_many :through to has_and_belongs_to_many.'
-  Enabled: false
+  Enabled: true
 
 Rails/Output:
   Description: 'Checks for calls to puts, print, etc.'
diff --git a/app/controllers/namespaces_controller.rb b/app/controllers/namespaces_controller.rb
index c59a2401cef..b7a9d8c1291 100644
--- a/app/controllers/namespaces_controller.rb
+++ b/app/controllers/namespaces_controller.rb
@@ -15,4 +15,3 @@ class NamespacesController < ApplicationController
     end
   end
 end
-
diff --git a/app/controllers/projects/raw_controller.rb b/app/controllers/projects/raw_controller.rb
index 84888265dc1..c4ddc32e8c3 100644
--- a/app/controllers/projects/raw_controller.rb
+++ b/app/controllers/projects/raw_controller.rb
@@ -35,4 +35,3 @@ class Projects::RawController < Projects::ApplicationController
     end
   end
 end
-
diff --git a/app/helpers/projects_helper.rb b/app/helpers/projects_helper.rb
index 687b087e683..5cec6ae99d8 100644
--- a/app/helpers/projects_helper.rb
+++ b/app/helpers/projects_helper.rb
@@ -254,4 +254,3 @@ module ProjectsHelper
     enabled_oauth_providers.include?(:github)
   end
 end
-
diff --git a/app/services/oauth2/access_token_validation_service.rb b/app/services/oauth2/access_token_validation_service.rb
index 5a3b94129f1..6194f6ce91e 100644
--- a/app/services/oauth2/access_token_validation_service.rb
+++ b/app/services/oauth2/access_token_validation_service.rb
@@ -38,4 +38,4 @@ module Oauth2::AccessTokenValidationService
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/config/initializers/7_omniauth.rb b/config/initializers/7_omniauth.rb
index 18759f0cfb0..8f6c5673103 100644
--- a/config/initializers/7_omniauth.rb
+++ b/config/initializers/7_omniauth.rb
@@ -9,4 +9,4 @@ if Gitlab::LDAP::Config.enabled?
     server = Gitlab.config.ldap.servers.values.first
     alias_method server['provider_name'], :ldap
   end
-end
\ No newline at end of file
+end
diff --git a/config/initializers/gitlab_shell_secret_token.rb b/config/initializers/gitlab_shell_secret_token.rb
index 8d2b771e535..e7c9f0ba7c2 100644
--- a/config/initializers/gitlab_shell_secret_token.rb
+++ b/config/initializers/gitlab_shell_secret_token.rb
@@ -16,4 +16,4 @@ end
 
 if File.exist?(Gitlab.config.gitlab_shell.path) && !File.exist?(gitlab_shell_symlink)
   FileUtils.symlink(secret_file, gitlab_shell_symlink)
-end
\ No newline at end of file
+end
diff --git a/lib/gitlab/backend/shell_adapter.rb b/lib/gitlab/backend/shell_adapter.rb
index f247f4593d7..fbe2a7a0d72 100644
--- a/lib/gitlab/backend/shell_adapter.rb
+++ b/lib/gitlab/backend/shell_adapter.rb
@@ -9,4 +9,3 @@ module Gitlab
     end
   end
 end
-
diff --git a/lib/gitlab/force_push_check.rb b/lib/gitlab/force_push_check.rb
index 6ba2c3ad00a..eae9773a067 100644
--- a/lib/gitlab/force_push_check.rb
+++ b/lib/gitlab/force_push_check.rb
@@ -12,4 +12,3 @@ module Gitlab
     end
   end
 end
-