diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 0000000..4c31b83
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,129 @@
+name: Test
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  test_sqlite:
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: [ '2.7', '3.0', '3.1' ]
+        rails: [ '6.0', '6.1', '7.0' ]
+
+    name: SQLite / Ruby ${{ matrix.ruby }} / Rails ${{ matrix.rails }}
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby }}
+
+    - name: Install gems
+      env:
+        MATRIX_RAILS_VERSION: ${{ matrix.rails }}
+      run: |
+        export BUNDLE_GEMFILE="${GITHUB_WORKSPACE}/gemfiles/rails_${MATRIX_RAILS_VERSION}.gemfile"
+        bundle install --jobs 4 --retry 3
+
+    - name: RSpec
+      run: bundle exec rake
+
+  test_mysql:
+    runs-on: ubuntu-latest
+
+    services:
+      mysql:
+        image: mysql:5.7
+        env:
+          MYSQL_ROOT_PASSWORD: password
+        ports:
+        - 3306:3306
+        options: >-
+          --health-cmd="mysqladmin ping"
+          --health-interval=10s
+          --health-timeout=5s
+          --health-retries=3
+
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: [ '2.7', '3.0', '3.1' ]
+        rails: [ '6.0', '6.1', '7.0' ]
+
+    name: MySQL / Ruby ${{ matrix.ruby }} / Rails ${{ matrix.rails }}
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby }}
+
+    - name: Install gems
+      env:
+        MATRIX_RAILS_VERSION: ${{ matrix.rails }}
+      run: |
+        export BUNDLE_GEMFILE="${GITHUB_WORKSPACE}/gemfiles/rails_${MATRIX_RAILS_VERSION}.gemfile"
+        bundle install --jobs 4 --retry 3
+
+    - name: Setup database
+      run: |
+        mysql -e 'create database IF NOT EXISTS unread_test;' -u root --password=password -P 3306 -h 127.0.0.1
+
+    - name: RSpec
+      run: bundle exec rake
+
+  test_postgres:
+    runs-on: ubuntu-latest
+
+    services:
+      postgres:
+        image: postgres
+        env:
+          POSTGRES_PASSWORD: postgres
+        options: >-
+          --health-cmd pg_isready
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+        ports:
+          - 5432:5432
+
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: [ '2.7', '3.0', '3.1' ]
+        rails: [ '6.0', '6.1', '7.0' ]
+
+    name: PostgreSQL / Ruby ${{ matrix.ruby }} / Rails ${{ matrix.rails }}
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby }}
+
+    - name: Install gems
+      env:
+        MATRIX_RAILS_VERSION: ${{ matrix.rails }}
+      run: |
+        export BUNDLE_GEMFILE="${GITHUB_WORKSPACE}/gemfiles/rails_${MATRIX_RAILS_VERSION}.gemfile"
+        bundle install --jobs 4 --retry 3
+
+    - name: Setup database
+      run: |
+        PGPASSWORD=postgres psql -c 'create database unread_test;' -U postgres -p 5432 -h localhost
+
+    - name: RSpec
+      run: bundle exec rake
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index d252172..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,44 +0,0 @@
-language: ruby
-rvm:
-  - 2.4.6
-  - 2.5.5
-  - 2.6.3
-gemfile:
-  - gemfiles/rails_6_0.gemfile
-  - gemfiles/rails_5_2.gemfile
-  - gemfiles/rails_5_1.gemfile
-  - gemfiles/rails_5_0.gemfile
-  - gemfiles/rails_4_2.gemfile
-  - gemfiles/rails_4_1.gemfile
-  - gemfiles/rails_4_0.gemfile
-matrix:
-  exclude:
-    - rvm: 2.4.6
-      gemfile: gemfiles/rails_4_0.gemfile
-    - rvm: 2.4.6
-      gemfile: gemfiles/rails_4_1.gemfile
-    - rvm: 2.4.6
-      gemfile: gemfiles/rails_6_0.gemfile
-    - rvm: 2.5.5
-      gemfile: gemfiles/rails_4_0.gemfile
-    - rvm: 2.5.5
-      gemfile: gemfiles/rails_4_1.gemfile
-    - rvm: 2.6.3
-      gemfile: gemfiles/rails_4_0.gemfile
-    - rvm: 2.6.3
-      gemfile: gemfiles/rails_4_1.gemfile
-before_install: gem update bundler
-sudo: false
-env:
-  - DB=sqlite
-  - DB=mysql
-  - DB=postgres
-services:
-  - mysql
-  - postgres
-before_script:
-  - gem update --system # https://github.com/travis-ci/travis-ci/issues/8978
-  - sh -c "if [ '$DB' = 'mysql' ]; then mysql -e 'create database IF NOT EXISTS unread_test;'; fi"
-  - sh -c "if [ '$DB' = 'postgres' ]; then psql -c 'create database unread_test;' -U postgres; fi"
-addons:
-  postgresql: "9.4"
diff --git a/Appraisals b/Appraisals
index 6eafe88..446bb36 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,48 +1,20 @@
-appraise "rails-6-0" do
-  gem "activerecord", "~> 6.0.0.beta3"
-  gem "mysql2", ">= 0.4.4"
-  gem "pg", ">= 0.18", "< 2.0"
+appraise "rails-7.0" do
+  gem "activerecord", "~> 7.0.0"
+  gem "mysql2", "~> 0.5"
+  gem "pg", "~> 1.1"
   gem "sqlite3", "~> 1.4"
 end
 
-appraise "rails-5-2" do
-  gem "activerecord", "~> 5.2.3"
-  gem "mysql2", ">= 0.4.4", "< 0.6.0"
-  gem "pg", ">= 0.18", "< 2.0"
-  gem "sqlite3", "~> 1.3", ">= 1.3.6"
-end
-
-appraise "rails-5-1" do
-  gem "activerecord", "~> 5.1.7"
-  gem "mysql2", ">= 0.3.18", "< 0.6.0"
-  gem "pg", ">= 0.18", "< 2.0"
-  gem "sqlite3", "~> 1.3", ">= 1.3.6"
+appraise "rails-6.1" do
+  gem "activerecord", "~> 6.1.2", ">= 6.1.2.1"
+  gem "mysql2", "~> 0.5"
+  gem "pg", "~> 1.1"
+  gem "sqlite3", "~> 1.4"
 end
 
-appraise "rails-5-0" do
-  gem "activerecord", "~> 5.0.7"
-  gem 'mysql2', '>= 0.3.18', '< 0.6.0'
+appraise "rails-6.0" do
+  gem "activerecord", "~> 6.0.0"
+  gem "mysql2", ">= 0.4.4"
   gem "pg", ">= 0.18", "< 2.0"
-  gem 'sqlite3', '~> 1.3.6'
-end
-
-appraise "rails-4-2" do
-  gem "activerecord", "~> 4.2.11"
-  gem 'mysql2', '>= 0.3.13', '< 0.6.0'
-  gem "pg", "~> 0.15"
-  gem 'sqlite3', '~> 1.3.6'
-end
-
-appraise "rails-4-1" do
-  gem "activerecord", "~> 4.1.16"
-  gem 'mysql2', '~> 0.3.13'
-  gem "pg", "~> 0.11"
-  gem 'sqlite3', '~> 1.3.6'
-end
-
-appraise "rails-4-0" do
-  gem "activerecord", "~> 4.0.13"
-  gem "mysql2", '~> 0.3.10'
-  gem "pg", "~> 0.11"
-  gem 'sqlite3', '~> 1.3.6'
+  gem "sqlite3", "~> 1.4"
 end
diff --git a/MIT-LICENSE b/MIT-LICENSE
index 11f8026..77416d9 100644
--- a/MIT-LICENSE
+++ b/MIT-LICENSE
@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2010-2019 Georg Ledermann
+Copyright (c) 2010-2022 Georg Ledermann
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the
diff --git a/README.md b/README.md
index b4df74d..3b8238b 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@ Unread
 
 Ruby gem to manage read/unread status of ActiveRecord objects - and it's fast.
 
-[![Build Status](https://travis-ci.org/ledermann/unread.svg?branch=master)](https://travis-ci.org/ledermann/unread)
+[![Build Status](https://github.com/ledermann/unread/workflows/Test/badge.svg?branch=master)](https://github.com/ledermann/unread/actions)
 [![Maintainability](https://api.codeclimate.com/v1/badges/930c8df0f99b20324444/maintainability)](https://codeclimate.com/github/ledermann/unread/maintainability)
 [![Coverage Status](https://coveralls.io/repos/ledermann/unread/badge.svg?branch=master)](https://coveralls.io/r/ledermann/unread?branch=master)
 
@@ -19,8 +19,8 @@ Ruby gem to manage read/unread status of ActiveRecord objects - and it's fast.
 
 ## Requirements
 
-* Ruby 2.4 or newer
-* Rails 4.0 or newer (including Rails 6)
+* Ruby 2.7 or newer
+* Rails 6.0 or newer (including Rails 7)
 * MySQL, PostgreSQL or SQLite
 * Needs a timestamp field in your models (like created_at or updated_at) with a database index on it
 
@@ -223,4 +223,4 @@ AND messages.created_at > '2010-10-20 08:50:00'
 Hint: You should add a database index on `messages.created_at`.
 
 
-Copyright (c) 2010-2019 [Georg Ledermann](http://www.georg-ledermann.de) and [contributors](https://github.com/ledermann/unread/graphs/contributors), released under the MIT license
+Copyright (c) 2010-2022 [Georg Ledermann](https://ledermann.dev) and [contributors](https://github.com/ledermann/unread/graphs/contributors), released under the MIT license
diff --git a/gemfiles/rails_4_0.gemfile b/gemfiles/rails_4_0.gemfile
deleted file mode 100644
index 3d1ccaf..0000000
--- a/gemfiles/rails_4_0.gemfile
+++ /dev/null
@@ -1,10 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 4.0.13"
-gem "mysql2", "~> 0.3.10"
-gem "pg", "~> 0.11"
-gem "sqlite3", "~> 1.3.6"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_4_1.gemfile b/gemfiles/rails_4_1.gemfile
deleted file mode 100644
index 6ede9af..0000000
--- a/gemfiles/rails_4_1.gemfile
+++ /dev/null
@@ -1,10 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 4.1.16"
-gem "mysql2", "~> 0.3.13"
-gem "pg", "~> 0.11"
-gem "sqlite3", "~> 1.3.6"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_4_2.gemfile b/gemfiles/rails_4_2.gemfile
deleted file mode 100644
index a7350b1..0000000
--- a/gemfiles/rails_4_2.gemfile
+++ /dev/null
@@ -1,10 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 4.2.11"
-gem "mysql2", ">= 0.3.13", "< 0.6.0"
-gem "pg", "~> 0.15"
-gem "sqlite3", "~> 1.3.6"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_5_0.gemfile b/gemfiles/rails_5_0.gemfile
deleted file mode 100644
index a2d1171..0000000
--- a/gemfiles/rails_5_0.gemfile
+++ /dev/null
@@ -1,10 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 5.0.7"
-gem "mysql2", ">= 0.3.18", "< 0.6.0"
-gem "pg", ">= 0.18", "< 2.0"
-gem "sqlite3", "~> 1.3.6"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_5_1.gemfile b/gemfiles/rails_5_1.gemfile
deleted file mode 100644
index bb41c09..0000000
--- a/gemfiles/rails_5_1.gemfile
+++ /dev/null
@@ -1,10 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 5.1.7"
-gem "mysql2", ">= 0.3.18", "< 0.6.0"
-gem "pg", ">= 0.18", "< 2.0"
-gem "sqlite3", "~> 1.3", ">= 1.3.6"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_5_2.gemfile b/gemfiles/rails_5_2.gemfile
deleted file mode 100644
index 9d1c2a6..0000000
--- a/gemfiles/rails_5_2.gemfile
+++ /dev/null
@@ -1,10 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 5.2.3"
-gem "mysql2", ">= 0.4.4", "< 0.6.0"
-gem "pg", ">= 0.18", "< 2.0"
-gem "sqlite3", "~> 1.3", ">= 1.3.6"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_6_0.gemfile b/gemfiles/rails_6.0.gemfile
similarity index 82%
rename from gemfiles/rails_6_0.gemfile
rename to gemfiles/rails_6.0.gemfile
index 54c91d5..2fd3073 100644
--- a/gemfiles/rails_6_0.gemfile
+++ b/gemfiles/rails_6.0.gemfile
@@ -2,7 +2,7 @@
 
 source "https://rubygems.org"
 
-gem "activerecord", "~> 6.0.0.beta3"
+gem "activerecord", "~> 6.0.0"
 gem "mysql2", ">= 0.4.4"
 gem "pg", ">= 0.18", "< 2.0"
 gem "sqlite3", "~> 1.4"
diff --git a/gemfiles/rails_6.1.gemfile b/gemfiles/rails_6.1.gemfile
new file mode 100644
index 0000000..b107a77
--- /dev/null
+++ b/gemfiles/rails_6.1.gemfile
@@ -0,0 +1,10 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 6.1.2", ">= 6.1.2.1"
+gem "mysql2", "~> 0.5"
+gem "pg", "~> 1.1"
+gem "sqlite3", "~> 1.4"
+
+gemspec path: "../"
diff --git a/gemfiles/rails_7.0.gemfile b/gemfiles/rails_7.0.gemfile
new file mode 100644
index 0000000..e4e22d0
--- /dev/null
+++ b/gemfiles/rails_7.0.gemfile
@@ -0,0 +1,10 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 7.0.0"
+gem "mysql2", "~> 0.5"
+gem "pg", "~> 1.1"
+gem "sqlite3", "~> 1.4"
+
+gemspec path: "../"
diff --git a/lib/generators/unread/migration/templates/migration.rb b/lib/generators/unread/migration/templates/migration.rb
index 098a51c..099e74b 100644
--- a/lib/generators/unread/migration/templates/migration.rb
+++ b/lib/generators/unread/migration/templates/migration.rb
@@ -1,9 +1,9 @@
-class UnreadMigration < Unread::MIGRATION_BASE_CLASS
+class UnreadMigration < ActiveRecord::Migration[6.0]
   def self.up
     create_table ReadMark, force: true, options: create_options do |t|
       t.references :readable, polymorphic: { null: false }
       t.references :reader,   polymorphic: { null: false }
-      t.datetime :timestamp
+      t.datetime :timestamp, null: false
     end
 
     add_index ReadMark, [:reader_id, :reader_type, :readable_type, :readable_id], name: 'read_marks_reader_readable_index', unique: true
diff --git a/lib/generators/unread/polymorphic_reader_migration/templates/unread_polymorphic_reader_migration.rb b/lib/generators/unread/polymorphic_reader_migration/templates/unread_polymorphic_reader_migration.rb
index 485d4da..2113659 100644
--- a/lib/generators/unread/polymorphic_reader_migration/templates/unread_polymorphic_reader_migration.rb
+++ b/lib/generators/unread/polymorphic_reader_migration/templates/unread_polymorphic_reader_migration.rb
@@ -1,4 +1,4 @@
-class UnreadPolymorphicReaderMigration < Unread::MIGRATION_BASE_CLASS
+class UnreadPolymorphicReaderMigration < ActiveRecord::Migration[6.0]
   def self.up
     remove_index :read_marks, [:user_id, :readable_type, :readable_id]
     rename_column :read_marks, :user_id, :reader_id
diff --git a/lib/unread.rb b/lib/unread.rb
index e617ebb..1ded71c 100644
--- a/lib/unread.rb
+++ b/lib/unread.rb
@@ -1,7 +1,6 @@
 require 'active_record'
 
 require 'unread/base'
-require 'unread/read_mark'
 require 'unread/readable'
 require 'unread/reader'
 require 'unread/readable_scopes'
@@ -9,10 +8,8 @@
 require 'unread/garbage_collector'
 require 'unread/version'
 
-ActiveRecord::Base.send :include, Unread
+ActiveSupport.on_load(:active_record) do
+  require 'unread/read_mark'
 
-Unread::MIGRATION_BASE_CLASS = if ActiveRecord::VERSION::MAJOR >= 5
-  ActiveRecord::Migration[5.0]
-else
-  ActiveRecord::Migration
+  include Unread
 end
diff --git a/lib/unread/base.rb b/lib/unread/base.rb
index 3cfa080..078da27 100644
--- a/lib/unread/base.rb
+++ b/lib/unread/base.rb
@@ -8,7 +8,7 @@ def acts_as_reader
       ReadMark.reader_classes ||= []
 
       unless ReadMark.reader_classes.include?(self)
-        ReadMark.belongs_to :reader, polymorphic: true, inverse_of: :read_marks
+        ReadMark.belongs_to :reader, polymorphic: true, inverse_of: :read_marks, optional: true
 
         has_many :read_marks, dependent: :delete_all, as: :reader, inverse_of: :reader
 
diff --git a/lib/unread/reader.rb b/lib/unread/reader.rb
index f526728..dce4e96 100644
--- a/lib/unread/reader.rb
+++ b/lib/unread/reader.rb
@@ -16,7 +16,13 @@ module InstanceMethods
       def read_mark_global(klass)
         @read_mark_global ||= {}
         readable_klass = klass.readable_parent
-        @read_mark_global[readable_klass] ||= read_marks.where(readable_type: readable_klass.name).global.first
+
+        # Memoize with NIL handling
+        if @read_mark_global.has_key?(readable_klass)
+          @read_mark_global[readable_klass]
+        else
+          @read_mark_global[readable_klass] = read_marks.where(readable_type: readable_klass.name).global.first
+        end
       end
 
       def forget_memoized_read_mark_global
diff --git a/lib/unread/version.rb b/lib/unread/version.rb
index e40b0f0..d88f91b 100644
--- a/lib/unread/version.rb
+++ b/lib/unread/version.rb
@@ -1,3 +1,3 @@
 module Unread
-  VERSION = '0.11.0'
+  VERSION = '0.12.0'
 end
diff --git a/spec/database.yml b/spec/database.yml
index d7bc521..139b8d9 100644
--- a/spec/database.yml
+++ b/spec/database.yml
@@ -5,8 +5,14 @@ mysql:
   adapter: mysql2
   database: unread_test
   username: root
+  password: password
   encoding: utf8
+  host: 127.0.0.1
+  port: 3306
 postgres:
   adapter: postgresql
   database: unread_test
   username: postgres
+  password: postgres
+  host: localhost
+  port: 5432
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 45f5c45..34fd217 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -64,7 +64,12 @@ def setup_db
   puts "Testing with ActiveRecord #{ActiveRecord::VERSION::STRING} on #{db_name}"
 
   ActiveRecord::Base.establish_connection(db_name.to_sym)
-  ActiveRecord::Base.default_timezone = :utc
+  if ActiveRecord.respond_to?(:default_timezone=)
+    # Rails 7
+    ActiveRecord.default_timezone = :utc
+  else
+    ActiveRecord::Base.default_timezone = :utc
+  end
   ActiveRecord::Migration.verbose = false
 
   UnreadMigration.up
diff --git a/spec/support/spec_migration.rb b/spec/support/spec_migration.rb
index eb641ec..70a2398 100644
--- a/spec/support/spec_migration.rb
+++ b/spec/support/spec_migration.rb
@@ -1,4 +1,4 @@
-class SpecMigration < Unread::MIGRATION_BASE_CLASS
+class SpecMigration < ActiveRecord::Migration[6.0]
   def self.up
     create_table Reader, primary_key: 'number', force: true do |t|
       t.string :name
diff --git a/spec/unread/readable_spec.rb b/spec/unread/readable_spec.rb
index c8add8c..ef275fc 100644
--- a/spec/unread/readable_spec.rb
+++ b/spec/unread/readable_spec.rb
@@ -253,6 +253,34 @@
 
       expect(@reader.read_marks.single.count).to eq 1
     end
+
+    context 'when the reader class defines a default_scope that excludes tha reader instance' do
+      before { ReadMark.stub(belongs_to_required_by_default: true) }
+
+      let!(:reader_class) do
+        CustomReader = Class.new(ActiveRecord::Base) do
+          self.primary_key = 'number'
+          self.table_name = 'readers'
+
+          acts_as_reader
+
+          default_scope { where.not(name: 'foo') }
+        end
+      end
+      let!(:reader) { reader_class.create!(name: 'foo') }
+      let(:document) { Document.create! }
+
+      before do
+        wait
+        document
+      end
+
+      subject { document.mark_as_read!(for: reader) }
+
+      it 'does not raise_error' do
+        expect { subject }.not_to raise_error
+      end
+    end
   end
 
   describe '.mark_as_read!' do
diff --git a/unread.gemspec b/unread.gemspec
index 97708ab..83525d8 100644
--- a/unread.gemspec
+++ b/unread.gemspec
@@ -8,11 +8,11 @@ Gem::Specification.new do |s|
   s.version     = Unread::VERSION
   s.licenses    = ['MIT']
   s.authors     = ["Georg Ledermann"]
-  s.email       = ["mail@georg-ledermann.de"]
+  s.email       = ["georg@ledermann.dev"]
   s.homepage    = "https://github.com/ledermann/unread"
   s.summary     = %q{Manages read/unread status of ActiveRecord objects}
   s.description = %q{This gem creates a scope for unread objects and adds methods to mark objects as read }
-  s.required_ruby_version = '>= 2.4'
+  s.required_ruby_version = '>= 2.7'
 
   s.files         = `git ls-files -z`.split("\x0").reject do |f|
     f.match(%r{^(test|spec|features)/})