diff --git a/.rubocop.yml b/.rubocop.yml
index aa0941b73..4b881bf27 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -36,22 +36,6 @@ Style/BlockDelimiters:
     - refute_silent
     - refute_throws
 
-# Offense count: 130
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: when_needed, always, never
-#
-# Description from Rubocop Manual:
-#   This cop is designed to help upgrade to Ruby 3.0. It will add the comment
-#   `# frozen_string_literal: true` to the top of files to enable frozen string
-#   literals. Frozen string literals may be default in Ruby 3.0. The comment
-#   will be added below a shebang and encoding comment. The frozen string
-#   literal comment is only valid in Ruby 2.3+.
-#
-# https://rubocop.readthedocs.io/en/latest/cops_style/#stylefrozenstringliteralcomment
-Style/FrozenStringLiteralComment:
-  Enabled: false
-
 # Offense count: 34
 # Cop supports --auto-correct.
 # Configuration parameters: AutoCorrect, EnforcedStyle.
diff --git a/Appraisals b/Appraisals
index c1fc4a8a2..2fde90088 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 [
   { name: '4-2', version: '4.2.10' }
 ].each do |rails|
diff --git a/Gemfile b/Gemfile
index b55a5d1d5..be8729b53 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
 
 # Declare your gem's dependencies in devise_token_auth.gemspec.
diff --git a/Guardfile b/Guardfile
index 1c909c3aa..24f70edd5 100644
--- a/Guardfile
+++ b/Guardfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # A sample Guardfile
 # More info at https://github.com/guard/guard#readme
 
diff --git a/bin/rails b/bin/rails
index de0283e9a..3ea4de6fc 100755
--- a/bin/rails
+++ b/bin/rails
@@ -1,4 +1,6 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
+
 # This command will automatically be run when you run "rails" with Rails 4 gems installed from the root of your application.
 
 ENGINE_ROOT = File.expand_path('..', __dir__)
diff --git a/devise_token_auth.gemspec b/devise_token_auth.gemspec
index f81649951..d87dc6714 100644
--- a/devise_token_auth.gemspec
+++ b/devise_token_auth.gemspec
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 $:.push File.expand_path('lib', __dir__)
 
 # Maintain your gem's version:
diff --git a/gemfiles/rails_4_2.gemfile b/gemfiles/rails_4_2.gemfile
index 3cfa680b5..cd9d3ee90 100644
--- a/gemfiles/rails_4_2.gemfile
+++ b/gemfiles/rails_4_2.gemfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file was generated by Appraisal
 
 source 'https://rubygems.org'
diff --git a/gemfiles/rails_5_0.gemfile b/gemfiles/rails_5_0.gemfile
index 0151565f7..e80236012 100644
--- a/gemfiles/rails_5_0.gemfile
+++ b/gemfiles/rails_5_0.gemfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file was generated by Appraisal
 
 source 'https://rubygems.org'
diff --git a/gemfiles/rails_5_1.gemfile b/gemfiles/rails_5_1.gemfile
index 6cad02f05..66af157ca 100644
--- a/gemfiles/rails_5_1.gemfile
+++ b/gemfiles/rails_5_1.gemfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file was generated by Appraisal
 
 source 'https://rubygems.org'
diff --git a/test/dummy/bin/bundle b/test/dummy/bin/bundle
index f19acf5b5..2dbb71769 100755
--- a/test/dummy/bin/bundle
+++ b/test/dummy/bin/bundle
@@ -1,3 +1,5 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
+
 ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
 load Gem.bin_path('bundler', 'bundle')
diff --git a/test/dummy/bin/rails b/test/dummy/bin/rails
index 1b99aac9c..666ce44df 100755
--- a/test/dummy/bin/rails
+++ b/test/dummy/bin/rails
@@ -1,4 +1,6 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
+
 begin
   load File.expand_path('spring', __dir__)
 rescue LoadError
diff --git a/test/dummy/bin/rake b/test/dummy/bin/rake
index 5a81e454b..fbda80b1d 100755
--- a/test/dummy/bin/rake
+++ b/test/dummy/bin/rake
@@ -1,4 +1,6 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
+
 begin
   load File.expand_path('spring', __dir__)
 rescue LoadError
diff --git a/test/dummy/bin/spring b/test/dummy/bin/spring
index ec62a6582..a019c01c0 100755
--- a/test/dummy/bin/spring
+++ b/test/dummy/bin/spring
@@ -1,4 +1,5 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
 
 # This file loads spring without using Bundler, in order to be fast
 # It gets overwritten when you run the `spring binstub` command
diff --git a/test/dummy/config.ru b/test/dummy/config.ru
index 2c4f92632..6270bcdfd 100644
--- a/test/dummy/config.ru
+++ b/test/dummy/config.ru
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file is used by Rack-based servers to start the application.
 
 require ::File.expand_path('../config/environment',  __FILE__)
diff --git a/test/dummy/db/schema.rb b/test/dummy/db/schema.rb
index 6012fe79f..7cb4e1a81 100644
--- a/test/dummy/db/schema.rb
+++ b/test/dummy/db/schema.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # This file is auto-generated from the current state of the database. Instead
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.