diff --git a/lib/redmine_admin_activity/models/custom_field_patch.rb b/lib/redmine_admin_activity/models/custom_field_patch.rb
index 357d732..e732649 100644
--- a/lib/redmine_admin_activity/models/custom_field_patch.rb
+++ b/lib/redmine_admin_activity/models/custom_field_patch.rb
@@ -12,7 +12,7 @@ def to_s
   end
 end
 
-class CustomField < ApplicationRecord
+class CustomField
   prepend RedmineAdminActivity::Models::CustomFieldPatch
 
   def self.representative_columns
diff --git a/lib/redmine_admin_activity/models/member_patch.rb b/lib/redmine_admin_activity/models/member_patch.rb
index f3b7005..8951b50 100644
--- a/lib/redmine_admin_activity/models/member_patch.rb
+++ b/lib/redmine_admin_activity/models/member_patch.rb
@@ -19,7 +19,7 @@ def update_project_journal
   end
 end
 
-class Member < ApplicationRecord
+class Member
   prepend RedmineAdminActivity::Models::MemberPatch
 
   attr_reader :project_journal
diff --git a/lib/redmine_admin_activity/models/project_patch.rb b/lib/redmine_admin_activity/models/project_patch.rb
index 46d0d7d..03f869d 100644
--- a/lib/redmine_admin_activity/models/project_patch.rb
+++ b/lib/redmine_admin_activity/models/project_patch.rb
@@ -37,7 +37,7 @@ def create_journal
   end
 end
 
-class Project < ApplicationRecord
+class Project
   prepend RedmineAdminActivity::Models::ProjectPatch
 
   acts_as_watchable
diff --git a/lib/redmine_admin_activity/models/version_patch.rb b/lib/redmine_admin_activity/models/version_patch.rb
index 4dfd181..4e3cd56 100644
--- a/lib/redmine_admin_activity/models/version_patch.rb
+++ b/lib/redmine_admin_activity/models/version_patch.rb
@@ -22,7 +22,7 @@ def save_previous_version
   end
 end
 
-class Version < ApplicationRecord
+class Version
   prepend RedmineAdminActivity::Models::VersionPatch
 
   before_update :save_previous_version