diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 151ff3d..7a760cc 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -84,6 +84,8 @@ jobs:
           gemfile: Gemfile.8.0.pg
         - ruby: 3.4.7
           gemfile: Gemfile.8.1.pg
+        - ruby: 4.0.1
+          gemfile: Gemfile.8.1.pg
 
     env:
       BUNDLE_GEMFILE: ${{ matrix.gemfile }}
diff --git a/Gemfile.8.1.pg.lock b/Gemfile.8.1.pg.lock
index 353849e..ca6c306 100644
--- a/Gemfile.8.1.pg.lock
+++ b/Gemfile.8.1.pg.lock
@@ -88,4 +88,4 @@ DEPENDENCIES
   rspec_candy
 
 BUNDLED WITH
-   2.7.2
+  4.0.4
diff --git a/spec/assignable_values/active_record_spec.rb b/spec/assignable_values/active_record_spec.rb
index 5123837..7b61991 100644
--- a/spec/assignable_values/active_record_spec.rb
+++ b/spec/assignable_values/active_record_spec.rb
@@ -1,5 +1,4 @@
 require 'spec_helper'
-require 'ostruct'
 
 def save_without_validation(record)
   if ActiveRecord::VERSION::MAJOR < 3