diff --git a/.github/workflows/rspec.yml b/.github/workflows/rspec.yml
index a6ab871..be508ec 100644
--- a/.github/workflows/rspec.yml
+++ b/.github/workflows/rspec.yml
@@ -16,49 +16,20 @@ jobs:
           - "3.2"
           - "3.1"
           - "3.0"
-          - "2.7"
-          - "2.6"
         gemfile:
+          - gemfiles/rails_8.0.gemfile
           - gemfiles/rails_7.2.gemfile
           - gemfiles/rails_7.1.gemfile
           - gemfiles/rails_7.0.gemfile
-          - gemfiles/rails_6.1.gemfile
-          - gemfiles/rails_6.0.gemfile
-          - gemfiles/rails_5.2.gemfile
         exclude:
-          - gemfile: gemfiles/rails_7.2.gemfile
-            ruby: "3.0"
-          - gemfile: gemfiles/rails_7.2.gemfile
-            ruby: "2.7"
-          - gemfile: gemfiles/rails_7.2.gemfile
-            ruby: "2.6"
-          - gemfile: gemfiles/rails_7.1.gemfile
-            ruby: "2.6"
-          - gemfile: gemfiles/rails_7.0.gemfile
-            ruby: "2.6"
-          - gemfile: gemfiles/rails_6.1.gemfile
-            ruby: "3.3"
-          - gemfile: gemfiles/rails_6.1.gemfile
-            ruby: "3.2"
-          - gemfile: gemfiles/rails_6.1.gemfile
+          - gemfile: gemfiles/rails_8.0.gemfile
             ruby: "3.1"
-          - gemfile: gemfiles/rails_6.0.gemfile
-            ruby: "3.3"
-          - gemfile: gemfiles/rails_6.0.gemfile
-            ruby: "3.2"
-          - gemfile: gemfiles/rails_6.0.gemfile
-            ruby: "3.1"
-          - gemfile: gemfiles/rails_6.0.gemfile
+          - gemfile: gemfiles/rails_8.0.gemfile
             ruby: "3.0"
-          - gemfile: gemfiles/rails_5.2.gemfile
-            ruby: "3.3"
-          - gemfile: gemfiles/rails_5.2.gemfile
-            ruby: "3.2"
-          - gemfile: gemfiles/rails_5.2.gemfile
-            ruby: "3.1"
-          - gemfile: gemfiles/rails_5.2.gemfile
+          - gemfile: gemfiles/rails_7.2.gemfile
             ruby: "3.0"
 
+
     env:
       BUNDLE_GEMFILE: ${{ format('{0}/{1}', github.workspace, matrix.gemfile) }}
       BUNDLE_PATH: ${{ format('{0}/vendor/bundle', github.workspace) }}
diff --git a/Appraisals b/Appraisals
index 84d6eea..a771a64 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,25 +1,17 @@
 # frozen_string_literal: true
 
-appraise "rails-5.2" do
-  gem 'activemodel', '~> 5.2.8.1'
-end
-
-appraise "rails-6.0" do
-  gem 'activemodel', '~> 6.0.6.1'
-end
-
-appraise "rails-6.1" do
-  gem 'activemodel', '~> 6.1.7.6'
-end
-
 appraise "rails-7.0" do
-  gem 'activemodel', '~> 7.0.8.4'
+  gem 'activemodel', '~> 7.0.8.6'
 end
 
 appraise "rails-7.1" do
-  gem 'activemodel', '~> 7.1.4'
+  gem 'activemodel', '~> 7.1.5'
 end
 
 appraise "rails-7.2" do
-  gem 'activemodel', '~> 7.2.1'
+  gem 'activemodel', '~> 7.2.2'
+end
+
+appraise "rails-8.0" do
+  gem 'activemodel', '~> 8.0.0'
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index fba761c..2a6d86d 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,7 +2,7 @@ PATH
   remote: .
   specs:
     nested_record (1.1.2)
-      activemodel (> 5.2, < 8.0)
+      activemodel (> 7.0, < 8.1)
 
 GEM
   remote: https://rubygems.org/
diff --git a/gemfiles/rails_5.2.gemfile.lock b/gemfiles/rails_5.2.gemfile.lock
deleted file mode 100644
index 69c1d13..0000000
--- a/gemfiles/rails_5.2.gemfile.lock
+++ /dev/null
@@ -1,57 +0,0 @@
-PATH
-  remote: ..
-  specs:
-    nested_record (1.1.2)
-      activemodel (> 5.2, < 8.0)
-
-GEM
-  remote: https://rubygems.org/
-  specs:
-    activemodel (5.2.8.1)
-      activesupport (= 5.2.8.1)
-    activesupport (5.2.8.1)
-      concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (>= 0.7, < 2)
-      minitest (~> 5.1)
-      tzinfo (~> 1.1)
-    appraisal (2.5.0)
-      bundler
-      rake
-      thor (>= 0.14.0)
-    concurrent-ruby (1.3.4)
-    diff-lcs (1.5.1)
-    i18n (1.14.5)
-      concurrent-ruby (~> 1.0)
-    minitest (5.25.1)
-    rake (13.2.1)
-    rspec (3.13.0)
-      rspec-core (~> 3.13.0)
-      rspec-expectations (~> 3.13.0)
-      rspec-mocks (~> 3.13.0)
-    rspec-core (3.13.1)
-      rspec-support (~> 3.13.0)
-    rspec-expectations (3.13.3)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.13.0)
-    rspec-mocks (3.13.1)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.13.0)
-    rspec-support (3.13.1)
-    thor (1.3.2)
-    thread_safe (0.3.6)
-    tzinfo (1.2.11)
-      thread_safe (~> 0.1)
-
-PLATFORMS
-  ruby
-
-DEPENDENCIES
-  activemodel (~> 5.2.8.1)
-  appraisal
-  bundler (>= 2)
-  nested_record!
-  rake (~> 13.0)
-  rspec (~> 3.0)
-
-BUNDLED WITH
-   2.3.22
diff --git a/gemfiles/rails_6.0.gemfile b/gemfiles/rails_6.0.gemfile
deleted file mode 100644
index 3073b40..0000000
--- a/gemfiles/rails_6.0.gemfile
+++ /dev/null
@@ -1,7 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activemodel", "~> 6.0.6.1"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_6.0.gemfile.lock b/gemfiles/rails_6.0.gemfile.lock
deleted file mode 100644
index a3f39e7..0000000
--- a/gemfiles/rails_6.0.gemfile.lock
+++ /dev/null
@@ -1,59 +0,0 @@
-PATH
-  remote: ..
-  specs:
-    nested_record (1.1.2)
-      activemodel (> 5.2, < 8.0)
-
-GEM
-  remote: https://rubygems.org/
-  specs:
-    activemodel (6.0.6.1)
-      activesupport (= 6.0.6.1)
-    activesupport (6.0.6.1)
-      concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (>= 0.7, < 2)
-      minitest (~> 5.1)
-      tzinfo (~> 1.1)
-      zeitwerk (~> 2.2, >= 2.2.2)
-    appraisal (2.5.0)
-      bundler
-      rake
-      thor (>= 0.14.0)
-    concurrent-ruby (1.3.4)
-    diff-lcs (1.5.1)
-    i18n (1.14.5)
-      concurrent-ruby (~> 1.0)
-    minitest (5.25.1)
-    rake (13.2.1)
-    rspec (3.13.0)
-      rspec-core (~> 3.13.0)
-      rspec-expectations (~> 3.13.0)
-      rspec-mocks (~> 3.13.0)
-    rspec-core (3.13.1)
-      rspec-support (~> 3.13.0)
-    rspec-expectations (3.13.3)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.13.0)
-    rspec-mocks (3.13.1)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.13.0)
-    rspec-support (3.13.1)
-    thor (1.3.2)
-    thread_safe (0.3.6)
-    tzinfo (1.2.11)
-      thread_safe (~> 0.1)
-    zeitwerk (2.6.18)
-
-PLATFORMS
-  ruby
-
-DEPENDENCIES
-  activemodel (~> 6.0.6.1)
-  appraisal
-  bundler (>= 2)
-  nested_record!
-  rake (~> 13.0)
-  rspec (~> 3.0)
-
-BUNDLED WITH
-   2.4.20
diff --git a/gemfiles/rails_6.1.gemfile b/gemfiles/rails_6.1.gemfile
deleted file mode 100644
index 64b942d..0000000
--- a/gemfiles/rails_6.1.gemfile
+++ /dev/null
@@ -1,7 +0,0 @@
-# This file was generated by Appraisal
-
-source "https://rubygems.org"
-
-gem "activemodel", "~> 6.1.7.6"
-
-gemspec path: "../"
diff --git a/gemfiles/rails_7.0.gemfile b/gemfiles/rails_7.0.gemfile
index 8864094..3aaabfc 100644
--- a/gemfiles/rails_7.0.gemfile
+++ b/gemfiles/rails_7.0.gemfile
@@ -2,6 +2,6 @@
 
 source "https://rubygems.org"
 
-gem "activemodel", "~> 7.0.8.4"
+gem "activemodel", "~> 7.0.8.6"
 
 gemspec path: "../"
diff --git a/gemfiles/rails_7.0.gemfile.lock b/gemfiles/rails_7.0.gemfile.lock
index 7672ff7..a5b32f4 100644
--- a/gemfiles/rails_7.0.gemfile.lock
+++ b/gemfiles/rails_7.0.gemfile.lock
@@ -2,14 +2,14 @@ PATH
   remote: ..
   specs:
     nested_record (1.1.2)
-      activemodel (> 5.2, < 8.0)
+      activemodel (> 7.0, < 8.1)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    activemodel (7.0.8.4)
-      activesupport (= 7.0.8.4)
-    activesupport (7.0.8.4)
+    activemodel (7.0.8.6)
+      activesupport (= 7.0.8.6)
+    activesupport (7.0.8.6)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
@@ -20,7 +20,7 @@ GEM
       thor (>= 0.14.0)
     concurrent-ruby (1.3.4)
     diff-lcs (1.5.1)
-    i18n (1.14.5)
+    i18n (1.14.6)
       concurrent-ruby (~> 1.0)
     minitest (5.25.1)
     rake (13.2.1)
@@ -28,12 +28,12 @@ GEM
       rspec-core (~> 3.13.0)
       rspec-expectations (~> 3.13.0)
       rspec-mocks (~> 3.13.0)
-    rspec-core (3.13.1)
+    rspec-core (3.13.2)
       rspec-support (~> 3.13.0)
     rspec-expectations (3.13.3)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
-    rspec-mocks (3.13.1)
+    rspec-mocks (3.13.2)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
     rspec-support (3.13.1)
@@ -45,7 +45,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  activemodel (~> 7.0.8.4)
+  activemodel (~> 7.0.8.6)
   appraisal
   bundler (>= 2)
   nested_record!
@@ -53,4 +53,4 @@ DEPENDENCIES
   rspec (~> 3.0)
 
 BUNDLED WITH
-   2.4.20
+   2.5.19
diff --git a/gemfiles/rails_7.1.gemfile b/gemfiles/rails_7.1.gemfile
index b515993..38696f3 100644
--- a/gemfiles/rails_7.1.gemfile
+++ b/gemfiles/rails_7.1.gemfile
@@ -2,6 +2,6 @@
 
 source "https://rubygems.org"
 
-gem "activemodel", "~> 7.1.4"
+gem "activemodel", "~> 7.1.5"
 
 gemspec path: "../"
diff --git a/gemfiles/rails_7.1.gemfile.lock b/gemfiles/rails_7.1.gemfile.lock
index 6c5ea31..b0e57a8 100644
--- a/gemfiles/rails_7.1.gemfile.lock
+++ b/gemfiles/rails_7.1.gemfile.lock
@@ -2,35 +2,40 @@ PATH
   remote: ..
   specs:
     nested_record (1.1.2)
-      activemodel (> 5.2, < 8.0)
+      activemodel (> 7.0, < 8.1)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    activemodel (7.1.4)
-      activesupport (= 7.1.4)
-    activesupport (7.1.4)
+    activemodel (7.1.5)
+      activesupport (= 7.1.5)
+    activesupport (7.1.5)
       base64
+      benchmark (>= 0.3)
       bigdecimal
       concurrent-ruby (~> 1.0, >= 1.0.2)
       connection_pool (>= 2.2.5)
       drb
       i18n (>= 1.6, < 2)
+      logger (>= 1.4.2)
       minitest (>= 5.1)
       mutex_m
+      securerandom (>= 0.3)
       tzinfo (~> 2.0)
     appraisal (2.5.0)
       bundler
       rake
       thor (>= 0.14.0)
     base64 (0.2.0)
+    benchmark (0.4.0)
     bigdecimal (3.1.8)
     concurrent-ruby (1.3.4)
     connection_pool (2.4.1)
     diff-lcs (1.5.1)
     drb (2.2.1)
-    i18n (1.14.5)
+    i18n (1.14.6)
       concurrent-ruby (~> 1.0)
+    logger (1.6.1)
     minitest (5.25.1)
     mutex_m (0.2.0)
     rake (13.2.1)
@@ -38,15 +43,16 @@ GEM
       rspec-core (~> 3.13.0)
       rspec-expectations (~> 3.13.0)
       rspec-mocks (~> 3.13.0)
-    rspec-core (3.13.1)
+    rspec-core (3.13.2)
       rspec-support (~> 3.13.0)
     rspec-expectations (3.13.3)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
-    rspec-mocks (3.13.1)
+    rspec-mocks (3.13.2)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
     rspec-support (3.13.1)
+    securerandom (0.3.1)
     thor (1.3.2)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
@@ -55,7 +61,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  activemodel (~> 7.1.4)
+  activemodel (~> 7.1.5)
   appraisal
   bundler (>= 2)
   nested_record!
@@ -63,4 +69,4 @@ DEPENDENCIES
   rspec (~> 3.0)
 
 BUNDLED WITH
-   2.4.20
+   2.5.19
diff --git a/gemfiles/rails_7.2.gemfile b/gemfiles/rails_7.2.gemfile
index 9aef0bb..70eb3a4 100644
--- a/gemfiles/rails_7.2.gemfile
+++ b/gemfiles/rails_7.2.gemfile
@@ -2,6 +2,6 @@
 
 source "https://rubygems.org"
 
-gem "activemodel", "~> 7.2.1"
+gem "activemodel", "~> 7.2.2"
 
 gemspec path: "../"
diff --git a/gemfiles/rails_7.2.gemfile.lock b/gemfiles/rails_7.2.gemfile.lock
index edf2851..28918bc 100644
--- a/gemfiles/rails_7.2.gemfile.lock
+++ b/gemfiles/rails_7.2.gemfile.lock
@@ -2,15 +2,16 @@ PATH
   remote: ..
   specs:
     nested_record (1.1.2)
-      activemodel (> 5.2, < 8.0)
+      activemodel (> 7.0, < 8.1)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    activemodel (7.2.1)
-      activesupport (= 7.2.1)
-    activesupport (7.2.1)
+    activemodel (7.2.2)
+      activesupport (= 7.2.2)
+    activesupport (7.2.2)
       base64
+      benchmark (>= 0.3)
       bigdecimal
       concurrent-ruby (~> 1.0, >= 1.3.1)
       connection_pool (>= 2.2.5)
@@ -25,12 +26,13 @@ GEM
       rake
       thor (>= 0.14.0)
     base64 (0.2.0)
+    benchmark (0.4.0)
     bigdecimal (3.1.8)
     concurrent-ruby (1.3.4)
     connection_pool (2.4.1)
     diff-lcs (1.5.1)
     drb (2.2.1)
-    i18n (1.14.5)
+    i18n (1.14.6)
       concurrent-ruby (~> 1.0)
     logger (1.6.1)
     minitest (5.25.1)
@@ -39,12 +41,12 @@ GEM
       rspec-core (~> 3.13.0)
       rspec-expectations (~> 3.13.0)
       rspec-mocks (~> 3.13.0)
-    rspec-core (3.13.1)
+    rspec-core (3.13.2)
       rspec-support (~> 3.13.0)
     rspec-expectations (3.13.3)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
-    rspec-mocks (3.13.1)
+    rspec-mocks (3.13.2)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
     rspec-support (3.13.1)
@@ -58,7 +60,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  activemodel (~> 7.2.1)
+  activemodel (~> 7.2.2)
   appraisal
   bundler (>= 2)
   nested_record!
@@ -66,4 +68,4 @@ DEPENDENCIES
   rspec (~> 3.0)
 
 BUNDLED WITH
-   2.5.5
+   2.5.19
diff --git a/gemfiles/rails_5.2.gemfile b/gemfiles/rails_8.0.gemfile
similarity index 74%
rename from gemfiles/rails_5.2.gemfile
rename to gemfiles/rails_8.0.gemfile
index 60ef567..41c8f7f 100644
--- a/gemfiles/rails_5.2.gemfile
+++ b/gemfiles/rails_8.0.gemfile
@@ -2,6 +2,6 @@
 
 source "https://rubygems.org"
 
-gem "activemodel", "~> 5.2.8.1"
+gem "activemodel", "~> 8.0.0"
 
 gemspec path: "../"
diff --git a/gemfiles/rails_6.1.gemfile.lock b/gemfiles/rails_8.0.gemfile.lock
similarity index 57%
rename from gemfiles/rails_6.1.gemfile.lock
rename to gemfiles/rails_8.0.gemfile.lock
index bb8d942..21caf28 100644
--- a/gemfiles/rails_6.1.gemfile.lock
+++ b/gemfiles/rails_8.0.gemfile.lock
@@ -2,52 +2,67 @@ PATH
   remote: ..
   specs:
     nested_record (1.1.2)
-      activemodel (> 5.2, < 8.0)
+      activemodel (> 7.0, < 8.1)
 
 GEM
   remote: https://rubygems.org/
   specs:
-    activemodel (6.1.7.8)
-      activesupport (= 6.1.7.8)
-    activesupport (6.1.7.8)
-      concurrent-ruby (~> 1.0, >= 1.0.2)
+    activemodel (8.0.0)
+      activesupport (= 8.0.0)
+    activesupport (8.0.0)
+      base64
+      benchmark (>= 0.3)
+      bigdecimal
+      concurrent-ruby (~> 1.0, >= 1.3.1)
+      connection_pool (>= 2.2.5)
+      drb
       i18n (>= 1.6, < 2)
+      logger (>= 1.4.2)
       minitest (>= 5.1)
-      tzinfo (~> 2.0)
-      zeitwerk (~> 2.3)
+      securerandom (>= 0.3)
+      tzinfo (~> 2.0, >= 2.0.5)
+      uri (>= 0.13.1)
     appraisal (2.5.0)
       bundler
       rake
       thor (>= 0.14.0)
+    base64 (0.2.0)
+    benchmark (0.4.0)
+    bigdecimal (3.1.8)
     concurrent-ruby (1.3.4)
+    connection_pool (2.4.1)
     diff-lcs (1.5.1)
-    i18n (1.14.5)
+    drb (2.2.1)
+    i18n (1.14.6)
       concurrent-ruby (~> 1.0)
+    logger (1.6.1)
     minitest (5.25.1)
     rake (13.2.1)
     rspec (3.13.0)
       rspec-core (~> 3.13.0)
       rspec-expectations (~> 3.13.0)
       rspec-mocks (~> 3.13.0)
-    rspec-core (3.13.1)
+    rspec-core (3.13.2)
       rspec-support (~> 3.13.0)
     rspec-expectations (3.13.3)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
-    rspec-mocks (3.13.1)
+    rspec-mocks (3.13.2)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.13.0)
     rspec-support (3.13.1)
+    securerandom (0.3.1)
     thor (1.3.2)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    zeitwerk (2.6.18)
+    uri (1.0.1)
 
 PLATFORMS
   ruby
+  x86_64-linux
 
 DEPENDENCIES
-  activemodel (~> 6.1.7.6)
+  activemodel (~> 8.0.0)
   appraisal
   bundler (>= 2)
   nested_record!
@@ -55,4 +70,4 @@ DEPENDENCIES
   rspec (~> 3.0)
 
 BUNDLED WITH
-   2.4.20
+   2.5.19
diff --git a/lib/nested_record/lookup_const.rb b/lib/nested_record/lookup_const.rb
index fef3a7b..95dccca 100644
--- a/lib/nested_record/lookup_const.rb
+++ b/lib/nested_record/lookup_const.rb
@@ -1,23 +1,12 @@
 # frozen_string_literal: true
 
 module NestedRecord
-  # TODO: Remove this when we drop support for Rails < 7.0
-  if ActiveSupport::VERSION::MAJOR < 7
-    def self.constantize(type_name)
-      ActiveSupport::Dependencies.constantize(type_name)
-    end
-
-    def self.safe_constantize(type_name)
-      ActiveSupport::Dependencies.safe_constantize(type_name)
-    end
-  else
-    def self.constantize(type_name)
-      type_name.constantize
-    end
+  def self.constantize(type_name)
+    type_name.constantize
+  end
 
-    def self.safe_constantize(type_name)
-      type_name.safe_constantize
-    end
+  def self.safe_constantize(type_name)
+    type_name.safe_constantize
   end
 
   # Derived from Rails source: https://github.com/rails/rails/blob/98a57aa5f610bc66af31af409c72173cdeeb3c9e/activerecord/lib/active_record/inheritance.rb#L181-L207
diff --git a/nested_record.gemspec b/nested_record.gemspec
index 08721a7..2c2d3e5 100644
--- a/nested_record.gemspec
+++ b/nested_record.gemspec
@@ -27,5 +27,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rspec", "~> 3.0"
   spec.add_development_dependency "appraisal"
 
-  spec.add_dependency "activemodel", "> 5.2", "< 8.0"
+  spec.add_dependency "activemodel", "> 7.0", "< 8.1"
 end