diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 54b9b5d..c325e4c 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -42,6 +42,7 @@ jobs:
         - gemfiles/rails_7_0.gemfile
         - gemfiles/rails_7_1.gemfile
         - gemfiles/rails_7_2.gemfile
+        - gemfiles/rails_8_0.gemfile
         - Gemfile
         - gemfiles/rails_head.gemfile
         exclude:
@@ -61,6 +62,8 @@ jobs:
           gemfile: gemfiles/rails_7_1.gemfile
         - ruby: "2.1"
           gemfile: gemfiles/rails_7_2.gemfile
+        - ruby: "2.1"
+          gemfile: gemfiles/rails_8_0.gemfile
         - ruby: "2.1"
           gemfile: Gemfile
         - ruby: "2.1"
@@ -75,6 +78,8 @@ jobs:
           gemfile: gemfiles/rails_7_1.gemfile
         - ruby: "2.2"
           gemfile: gemfiles/rails_7_2.gemfile
+        - ruby: "2.2"
+          gemfile: gemfiles/rails_8_0.gemfile
         - ruby: "2.2"
           gemfile: Gemfile
         - ruby: "2.2"
@@ -89,6 +94,8 @@ jobs:
           gemfile: gemfiles/rails_7_1.gemfile
         - ruby: "2.3"
           gemfile: gemfiles/rails_7_2.gemfile
+        - ruby: "2.3"
+          gemfile: gemfiles/rails_8_0.gemfile
         - ruby: "2.3"
           gemfile: Gemfile
         - ruby: "2.3"
@@ -103,6 +110,8 @@ jobs:
           gemfile: gemfiles/rails_7_1.gemfile
         - ruby: "2.4"
           gemfile: gemfiles/rails_7_2.gemfile
+        - ruby: "2.4"
+          gemfile: gemfiles/rails_8_0.gemfile
         - ruby: "2.4"
           gemfile: Gemfile
         - ruby: "2.4"
@@ -117,6 +126,8 @@ jobs:
           gemfile: gemfiles/rails_7_1.gemfile
         - ruby: "2.5"
           gemfile: gemfiles/rails_7_2.gemfile
+        - ruby: "2.5"
+          gemfile: gemfiles/rails_8_0.gemfile
         - ruby: "2.5"
           gemfile: Gemfile
         - ruby: "2.5"
@@ -131,6 +142,8 @@ jobs:
           gemfile: gemfiles/rails_7_1.gemfile
         - ruby: "2.6"
           gemfile: gemfiles/rails_7_2.gemfile
+        - ruby: "2.6"
+          gemfile: gemfiles/rails_8_0.gemfile
         - ruby: "2.6"
           gemfile: Gemfile
         - ruby: "2.6"
@@ -149,6 +162,8 @@ jobs:
           gemfile: gemfiles/rails_4_2.gemfile
         - ruby: "2.7"
           gemfile: gemfiles/rails_7_2.gemfile
+        - ruby: "2.7"
+          gemfile: gemfiles/rails_8_0.gemfile
         - ruby: "2.7"
           gemfile: Gemfile
         - ruby: "2.7"
@@ -173,6 +188,8 @@ jobs:
           gemfile: gemfiles/rails_5_2.gemfile
         - ruby: "3.0"
           gemfile: gemfiles/rails_7_2.gemfile
+        - ruby: "3.0"
+          gemfile: gemfiles/rails_8_0.gemfile
         - ruby: "3.0"
           gemfile: Gemfile
         - ruby: "3.0"
@@ -195,6 +212,10 @@ jobs:
           gemfile: gemfiles/rails_5_1.gemfile
         - ruby: "3.1"
           gemfile: gemfiles/rails_5_2.gemfile
+        - ruby: "3.1"
+          gemfile: gemfiles/rails_8_0.gemfile
+        - ruby: "3.1"
+          gemfile: Gemfile
         - ruby: "3.1"
           gemfile: gemfiles/rails_head.gemfile
         - ruby: "3.2"
diff --git a/active_attr.gemspec b/active_attr.gemspec
index 50d0604..42ecbbf 100644
--- a/active_attr.gemspec
+++ b/active_attr.gemspec
@@ -22,9 +22,9 @@ Gem::Specification.new do |gem|
 
   gem.required_ruby_version = ">= 2.1.0"
 
-  gem.add_runtime_dependency "actionpack",    ">= 3.0.2", "< 8.0"
-  gem.add_runtime_dependency "activemodel",   ">= 3.0.2", "< 8.0"
-  gem.add_runtime_dependency "activesupport", ">= 3.0.2", "< 8.0"
+  gem.add_runtime_dependency "actionpack",    ">= 3.0.2", "< 9.0"
+  gem.add_runtime_dependency "activemodel",   ">= 3.0.2", "< 9.0"
+  gem.add_runtime_dependency "activesupport", ">= 3.0.2", "< 9.0"
 
   gem.add_development_dependency "bundler"
   gem.add_development_dependency "factory_bot",  "< 7.0"
diff --git a/gemfiles/rails_8_0.gemfile b/gemfiles/rails_8_0.gemfile
new file mode 100644
index 0000000..6922191
--- /dev/null
+++ b/gemfiles/rails_8_0.gemfile
@@ -0,0 +1,10 @@
+source "https://rubygems.org"
+
+gemspec :development_group => :test, :path => ".."
+
+gem "activemodel",   "~> 8.0.0"
+gem "activesupport", "~> 8.0.0"
+gem "actionpack",    "~> 8.0.0"
+gem "activemodel-serializers-xml", :group => :test
+gem "rexml", :group => :test
+gem "protected_attributes_continued", :group => :test