diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 0000000..dc07643
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,153 @@
+name: Test
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  test_sqlite:
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: ['3.1', '3.2', '3.3', '3.4']
+        rails: ['6.1', '7.0', '7.1', '7.2']
+        exclude:
+          - ruby: 3.4
+            rails: 6.1
+          - ruby: 3.4
+            rails: 7.0
+
+    name: SQLite / Ruby ${{ matrix.ruby }} / Rails ${{ matrix.rails }}
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - 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
+      env:
+        COVERALLS_REPO_TOKEN: ${{ secrets.COVERALLS_REPO_TOKEN }}
+        DB: sqlite
+      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: ['3.1', '3.2', '3.3', '3.4']
+        rails: ['6.1', '7.0', '7.1', '7.2']
+        exclude:
+          - ruby: 3.4
+            rails: 6.1
+          - ruby: 3.4
+            rails: 7.0
+
+    name: MySQL / Ruby ${{ matrix.ruby }} / Rails ${{ matrix.rails }}
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - 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
+      env:
+        COVERALLS_REPO_TOKEN: ${{ secrets.COVERALLS_REPO_TOKEN }}
+        DB: mysql
+      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: ['3.1', '3.2', '3.3', '3.4']
+        rails: ['6.1', '7.0', '7.1', '7.2']
+        exclude:
+          - ruby: 3.4
+            rails: 6.1
+          - ruby: 3.4
+            rails: 7.0
+
+    name: PostgreSQL / Ruby ${{ matrix.ruby }} / Rails ${{ matrix.rails }}
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - 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
+      env:
+        COVERALLS_REPO_TOKEN: ${{ secrets.COVERALLS_REPO_TOKEN }}
+        DB: postgres
+      run: bundle exec rake
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index b1bd327..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,33 +0,0 @@
-language: ruby
-rvm:
-  - 2.2.9
-  - 2.3.6
-  - 2.4.3
-  - 2.5.0
-gemfile:
-  - gemfiles/rails_5_2.gemfile
-  - gemfiles/rails_5_1.gemfile
-  - gemfiles/rails_5_0.gemfile
-  - gemfiles/rails_4_2.gemfile
-  - gemfiles/rails_4_1.gemfile
-  - gemfiles/rails_4_0.gemfile
-matrix:
-  exclude:
-    - rvm: 2.4.3
-      gemfile: gemfiles/rails_4_0.gemfile
-    - rvm: 2.4.3
-      gemfile: gemfiles/rails_4_1.gemfile
-    - rvm: 2.5.0
-      gemfile: gemfiles/rails_4_0.gemfile
-    - rvm: 2.5.0
-      gemfile: gemfiles/rails_4_1.gemfile
-before_install: gem update bundler
-sudo: false
-env:
-  - DB=sqlite
-  - DB=mysql
-  - DB=postgres
-before_script:
-  - gem update --system # https://github.com/travis-ci/travis-ci/issues/8978
-  - sh -c "if [ '$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"
diff --git a/Appraisals b/Appraisals
index 547e4f9..17deb80 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,29 +1,27 @@
-appraise "rails-5-2" do
-  gem "activerecord", "~> 5.2.0.beta2"
-  gem "mysql2", ">= 0.3.18", "< 0.5", "!= 0.4.3"
+appraise "rails-7.2" do
+  gem "activerecord", "~> 7.2.0"
+  gem "mysql2", "~> 0.5"
+  gem "pg", "~> 1.3"
+  gem "sqlite3", ">= 2.0"
 end
 
-appraise "rails-5-1" do
-  gem "activerecord", "~> 5.1.0"
-  gem 'mysql2', '>= 0.3.18', '< 0.5'
+appraise "rails-7.1" do
+  gem "activerecord", "~> 7.1.0"
+  gem "mysql2", "~> 0.5"
+  gem "pg", "~> 1.3"
+  gem "sqlite3", "~> 1.4"
 end
 
-appraise "rails-5-0" do
-  gem "activerecord", "~> 5.0.0"
-  gem 'mysql2', '>= 0.3.18', '< 0.5'
+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-4-2" do
-  gem "activerecord", "~> 4.2.5"
-  gem 'mysql2', '>= 0.3.13', '< 0.5'
-end
-
-appraise "rails-4-1" do
-  gem "activerecord", "~> 4.1.14"
-  gem "mysql2", '~> 0.3.13'
-end
-
-appraise "rails-4-0" do
-  gem "activerecord", "~> 4.0.13"
-  gem "mysql2", '~> 0.3.10'
+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
diff --git a/MIT-LICENSE b/MIT-LICENSE
index 3d98d42..75c4e85 100644
--- a/MIT-LICENSE
+++ b/MIT-LICENSE
@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2010-2018 Georg Ledermann
+Copyright (c) 2010-2023 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 5a1e86e..b8e0e02 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 2.2 or newer
-* Rails 4.0 or newer (including Rails 5.1 and 5.2)
+* Ruby 3.1 or newer
+* Rails 6.1 or newer (including Rails 7.2)
 * MySQL, PostgreSQL or SQLite
 * Needs a timestamp field in your models (like created_at or updated_at) with a database index on it
 
@@ -160,6 +160,30 @@ users[1].have_read?(message2)
 Message.cleanup_read_marks!
 ```
 
+## Getting read/unread stats through a relationship
+
+```ruby
+class Document < ApplicationRecord
+  has_many :comments
+end
+
+class Comment < ApplicationRecord
+  acts_as_readable on: :created_at
+  belongs_to :document
+end
+
+# Get unread comments count for a document
+document = Document.find(1)
+default_hash = Hash.new { |h, k| h[k] = { unread: 0, total: 0 } }
+document.comments.with_read_marks_for(current_user).reduce(default_hash) do |hash, comment|
+  hash[comment.id][:unread] += 1 if comment.unread?(current_user)
+  hash[comment.id][:total] += 1
+  hash
+end
+# => {20=>{:unread=>1, :total=>10}, 82=>{:unread=>0, :total=>4}
+```
+
+Using `with_read_marks_for` here is the key. It uses just one query and makes sure that the following `unread?` invocations use the result of the first query.
 
 ## How does it work?
 
@@ -199,4 +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) 2010-2018 [Georg Ledermann](http://www.georg-ledermann.de) and [contributors](https://github.com/ledermann/unread/graphs/contributors), released under the MIT license
+Copyright (c) 2010-2023 [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 c319a35..0000000
--- a/gemfiles/rails_4_0.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 4.0.13"
-gem "mysql2", "~> 0.3.10"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_4_1.gemfile b/gemfiles/rails_4_1.gemfile
deleted file mode 100644
index 79165aa..0000000
--- a/gemfiles/rails_4_1.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 4.1.14"
-gem "mysql2", "~> 0.3.13"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_4_2.gemfile b/gemfiles/rails_4_2.gemfile
deleted file mode 100644
index 7a7908b..0000000
--- a/gemfiles/rails_4_2.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 4.2.5"
-gem "mysql2", ">= 0.3.13", "< 0.5"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_5_0.gemfile b/gemfiles/rails_5_0.gemfile
deleted file mode 100644
index f7dfd7f..0000000
--- a/gemfiles/rails_5_0.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 5.0.0"
-gem "mysql2", ">= 0.3.18", "< 0.5"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_5_1.gemfile b/gemfiles/rails_5_1.gemfile
deleted file mode 100644
index 979beae..0000000
--- a/gemfiles/rails_5_1.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 5.1.0"
-gem "mysql2", ">= 0.3.18", "< 0.5"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_5_2.gemfile b/gemfiles/rails_5_2.gemfile
deleted file mode 100644
index ae456ee..0000000
--- a/gemfiles/rails_5_2.gemfile
+++ /dev/null
@@ -1,8 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activerecord", "~> 5.2.0.beta2"
-gem "mysql2", ">= 0.3.18", "< 0.5", "!= 0.4.3"
-
-gemspec path: "../"
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/gemfiles/rails_7.1.gemfile b/gemfiles/rails_7.1.gemfile
new file mode 100644
index 0000000..b155949
--- /dev/null
+++ b/gemfiles/rails_7.1.gemfile
@@ -0,0 +1,10 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 7.1.0"
+gem "mysql2", "~> 0.5"
+gem "pg", "~> 1.3"
+gem "sqlite3", "~> 1.4"
+
+gemspec path: "../"
diff --git a/gemfiles/rails_7.2.gemfile b/gemfiles/rails_7.2.gemfile
new file mode 100644
index 0000000..8254482
--- /dev/null
+++ b/gemfiles/rails_7.2.gemfile
@@ -0,0 +1,10 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 7.2.0"
+gem "mysql2", "~> 0.5"
+gem "pg", "~> 1.3"
+gem "sqlite3", ">= 2.0"
+
+gemspec path: "../"
diff --git a/lib/generators/unread/migration/migration_generator.rb b/lib/generators/unread/migration/migration_generator.rb
index e197c9b..3684340 100644
--- a/lib/generators/unread/migration/migration_generator.rb
+++ b/lib/generators/unread/migration/migration_generator.rb
@@ -13,11 +13,22 @@ def create_migration_file
     end
 
     def self.next_migration_number(dirname)
-      if ActiveRecord::Base.timestamped_migrations
+      if self.timestamped_migrations?
         Time.now.utc.strftime("%Y%m%d%H%M%S")
       else
         "%.3d" % (current_migration_number(dirname) + 1)
       end
     end
+
+    def self.timestamped_migrations?
+      (
+        ActiveRecord::Base.respond_to?(:timestamped_migrations) &&
+          ActiveRecord::Base.timestamped_migrations
+      ) ||
+        (
+          ActiveRecord.respond_to?(:timestamped_migrations) &&
+            ActiveRecord.timestamped_migrations
+        )
+    end
   end
 end
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/polymorphic_reader_migration_generator.rb b/lib/generators/unread/polymorphic_reader_migration/polymorphic_reader_migration_generator.rb
index 05e0f2d..b865ac6 100644
--- a/lib/generators/unread/polymorphic_reader_migration/polymorphic_reader_migration_generator.rb
+++ b/lib/generators/unread/polymorphic_reader_migration/polymorphic_reader_migration_generator.rb
@@ -13,11 +13,22 @@ def create_migration_file
     end
 
     def self.next_migration_number(dirname)
-      if ActiveRecord::Base.timestamped_migrations
-        Time.now.utc.strftime("%Y%m%d%H%M%S")
+      if self.timestamped_migrations?
+        Time.now.utc.strftime('%Y%m%d%H%M%S')
       else
         "%.3d" % (current_migration_number(dirname) + 1)
       end
     end
+
+    def self.timestamped_migrations?
+      (
+        ActiveRecord::Base.respond_to?(:timestamped_migrations) &&
+          ActiveRecord::Base.timestamped_migrations
+      ) ||
+        (
+          ActiveRecord.respond_to?(:timestamped_migrations) &&
+            ActiveRecord.timestamped_migrations
+        )
+    end
   end
 end
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/readable_scopes.rb b/lib/unread/readable_scopes.rb
index ca1ca4d..eeff7b1 100644
--- a/lib/unread/readable_scopes.rb
+++ b/lib/unread/readable_scopes.rb
@@ -7,8 +7,8 @@ def join_read_marks(reader)
         joins "LEFT JOIN #{ReadMark.quoted_table_name}
                 ON #{ReadMark.quoted_table_name}.readable_type  = '#{readable_parent.name}'
                AND #{ReadMark.quoted_table_name}.readable_id    = #{quoted_table_name}.#{quoted_primary_key}
-               AND #{ReadMark.quoted_table_name}.reader_id      = #{quote_bound_value(reader.id)}
-               AND #{ReadMark.quoted_table_name}.reader_type    = #{quote_bound_value(reader.class.base_class.name)}
+               AND #{ReadMark.quoted_table_name}.reader_id      = #{quoted(reader.id)}
+               AND #{ReadMark.quoted_table_name}.reader_type    = #{quoted(reader.class.base_class.name)}
                AND #{ReadMark.quoted_table_name}.timestamp     >= #{quoted_table_name}.#{connection.quote_column_name(readable_options[:on])}"
       end
 
@@ -39,8 +39,16 @@ def with_read_marks_for(reader)
 
         join_read_marks(reader).select("#{quoted_table_name}.*,
                                         #{ReadMark.quoted_table_name}.id AS read_mark_id,
-                                        #{quote_bound_value(reader.class.base_class.name)}#{postgresql_string_cast} AS read_mark_reader_type,
-                                        #{quote_bound_value(reader.id)} AS read_mark_reader_id")
+                                        #{quoted(reader.class.base_class.name)}#{postgresql_string_cast} AS read_mark_reader_type,
+                                        #{quoted(reader.id)} AS read_mark_reader_id")
+      end
+
+      def quoted(value)
+        if Gem::Version.new(ActiveRecord::VERSION::STRING) >= Gem::Version.new('7.2')
+          quote_bound_value(connection, value)
+        else
+          quote_bound_value(value)
+        end
       end
     end
   end
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/reader_scopes.rb b/lib/unread/reader_scopes.rb
index b6936c8..00a4831 100644
--- a/lib/unread/reader_scopes.rb
+++ b/lib/unread/reader_scopes.rb
@@ -12,7 +12,7 @@ def join_read_marks(readable)
 
         joins "LEFT JOIN #{ReadMark.quoted_table_name}
                 ON #{ReadMark.quoted_table_name}.readable_type  = '#{readable.class.readable_parent.name}'
-               AND (#{ReadMark.quoted_table_name}.readable_id   = #{readable.id} OR #{ReadMark.quoted_table_name}.readable_id IS NULL)
+               AND (#{ReadMark.quoted_table_name}.readable_id   = #{quoted(readable.id)} OR #{ReadMark.quoted_table_name}.readable_id IS NULL)
                AND #{ReadMark.quoted_table_name}.reader_id      = #{quoted_table_name}.#{quoted_primary_key}
                AND #{ReadMark.quoted_table_name}.reader_type    = '#{connection.quote_string base_class.name}'
                AND #{ReadMark.quoted_table_name}.timestamp     >= '#{connection.quoted_date readable.send(readable.class.readable_options[:on])}'"
@@ -31,8 +31,16 @@ def with_read_marks_for(readable)
 
         join_read_marks(readable).select("#{quoted_table_name}.*,
                                           #{ReadMark.quoted_table_name}.id AS read_mark_id,
-                                          #{quote_bound_value readable.class.name}#{postgresql_string_cast} AS read_mark_readable_type,
-                                          #{readable.id} AS read_mark_readable_id")
+                                          #{quoted(readable.class.name)}#{postgresql_string_cast} AS read_mark_readable_type,
+                                          #{quoted(readable.id)} AS read_mark_readable_id")
+      end
+
+      def quoted(value)
+        if Gem::Version.new(ActiveRecord::VERSION::STRING) >= Gem::Version.new('7.2')
+          quote_bound_value(connection, value)
+        else
+          quote_bound_value(value)
+        end
       end
     end
   end
diff --git a/lib/unread/version.rb b/lib/unread/version.rb
index d1da520..5008351 100644
--- a/lib/unread/version.rb
+++ b/lib/unread/version.rb
@@ -1,3 +1,3 @@
 module Unread
-  VERSION = '0.10.1'
+  VERSION = '0.14.0'
 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 b742b74..ef275fc 100644
--- a/spec/unread/readable_spec.rb
+++ b/spec/unread/readable_spec.rb
@@ -195,7 +195,7 @@
       wait
       expect(@email1.unread?(@reader)).to be_falsey
 
-      @email1.update_attributes! subject: 'changed'
+      @email1.update! subject: 'changed'
       expect(@email1.unread?(@reader)).to be_truthy
     end
 
@@ -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/spec/unread/reader_spec.rb b/spec/unread/reader_spec.rb
index 5f0fea0..05cb0a4 100644
--- a/spec/unread/reader_spec.rb
+++ b/spec/unread/reader_spec.rb
@@ -149,7 +149,7 @@
       wait
       expect(@reader.have_read?(@email1)).to be_truthy
 
-      @email1.update_attributes! subject: 'changed'
+      @email1.update! subject: 'changed'
       expect(@reader.have_read?(@email1)).to be_falsey
     end
 
diff --git a/unread.gemspec b/unread.gemspec
index 7f7b982..3dcfbca 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 = '>= 2.2'
+  s.required_ruby_version = '>= 3.1'
 
   s.files         = `git ls-files -z`.split("\x0").reject do |f|
     f.match(%r{^(test|spec|features)/})
@@ -21,17 +21,17 @@ Gem::Specification.new do |s|
   s.executables   = s.files.grep(%r{^exe/}) { |f| File.basename(f) }
   s.require_paths = ["lib"]
 
-  s.add_dependency 'activerecord', '>= 3'
+  s.add_dependency 'activerecord', '>= 6.1'
 
   s.add_development_dependency 'bundler'
   s.add_development_dependency 'rake'
   s.add_development_dependency 'timecop'
   s.add_development_dependency 'sqlite3'
   s.add_development_dependency 'mysql2'
-  s.add_development_dependency 'pg', '< 1'
+  s.add_development_dependency 'pg'
   s.add_development_dependency 'rspec'
   s.add_development_dependency 'simplecov'
   s.add_development_dependency 'term-ansicolor'
-  s.add_development_dependency 'coveralls'
+  s.add_development_dependency 'coveralls_reborn'
   s.add_development_dependency 'appraisal'
 end