diff --git a/activerecord/test/cases/attributes_test.rb b/activerecord/test/cases/attributes_test.rb
index f4620ae2da..5874a09f86 100644
--- a/activerecord/test/cases/attributes_test.rb
+++ b/activerecord/test/cases/attributes_test.rb
@@ -106,12 +106,14 @@ class CustomPropertiesTest < ActiveRecord::TestCase
 
       assert_equal 6, klass.attribute_types.length
       assert_equal 6, klass.column_defaults.length
+      assert_equal 6, klass.attribute_names.length
       assert_not klass.attribute_types.include?("wibble")
 
       klass.attribute :wibble, Type::Value.new
 
       assert_equal 7, klass.attribute_types.length
       assert_equal 7, klass.column_defaults.length
+      assert_equal 7, klass.attribute_names.length
       assert_includes klass.attribute_types, "wibble"
     end