diff --git a/db/seeds.rb b/db/seeds.rb
index 276edb19..77e208ac 100644
--- a/db/seeds.rb
+++ b/db/seeds.rb
@@ -9,19 +9,19 @@
     .create!(
       messageable_type: messageable_type,
       messageable_id: messageable_id,
-      status: Outboxer::Models::Message::STATUS[:unpublished])
+      status: Outboxer::Models::Message::Status::UNPUBLISHED)
 
   Outboxer::Models::Message
     .create!(
       messageable_type: messageable_type,
       messageable_id: messageable_id,
-      status: Outboxer::Models::Message::STATUS[:publishing])
+      status: Outboxer::Models::Message::Status::PUBLISHING)
 
   failed_message = Outboxer::Models::Message
     .create!(
       messageable_type: messageable_type,
       messageable_id: messageable_id,
-      status: Outboxer::Models::Message::STATUS[:failed])
+      status: Outboxer::Models::Message::Status::FAILED)
 
   failed_message
     .outboxer_exceptions
diff --git a/lib/outboxer/message.rb b/lib/outboxer/message.rb
index 50b2f9d4..47e6a090 100644
--- a/lib/outboxer/message.rb
+++ b/lib/outboxer/message.rb
@@ -13,21 +13,21 @@ def unpublished!(limit: 5, order: :asc)
       ActiveRecord::Base.connection_pool.with_connection do
         message_ids = ActiveRecord::Base.transaction do
           ids = Models::Message
-            .where(status: Models::Message::STATUS[:unpublished])
+            .where(status: Models::Message::Status::UNPUBLISHED)
             .order(created_at: order)
             .lock('FOR UPDATE SKIP LOCKED')
             .limit(limit)
             .pluck(:id)
 
           if !ids.empty?
-            Models::Message.where(id: ids).update_all(status: Models::Message::STATUS[:publishing])
+            Models::Message.where(id: ids).update_all(status: Models::Message::Status::PUBLISHING)
           end
 
           ids
         end
 
         Models::Message
-          .where(id: message_ids, status: Models::Message::STATUS[:publishing])
+          .where(id: message_ids, status: Models::Message::Status::PUBLISHING)
           .order(created_at: order)
           .to_a
       end
@@ -37,7 +37,7 @@ def published!(id:)
       ActiveRecord::Base.connection_pool.with_connection do
         outboxer_message = Models::Message.order(created_at: :asc).lock.find_by!(id: id)
 
-        if outboxer_message.status != Models::Message::STATUS[:publishing]
+        if outboxer_message.status != Models::Message::Status::PUBLISHING
           raise InvalidTransition,
             "cannot transition outboxer message #{outboxer_message.id} " \
             "from #{outboxer_message.status} to (deleted)"
@@ -54,13 +54,13 @@ def failed!(id:, exception:)
         ActiveRecord::Base.transaction do
           outboxer_message = Models::Message.order(created_at: :asc).lock.find_by!(id: id)
 
-          if outboxer_message.status != Models::Message::STATUS[:publishing]
+          if outboxer_message.status != Models::Message::Status::PUBLISHING
             raise InvalidTransition,
               "cannot transition outboxer message #{id} " \
-              "from #{outboxer_message.status} to #{Models::Message::STATUS[:failed]}"
+              "from #{outboxer_message.status} to #{Models::Message::Status::FAILED}"
           end
 
-          outboxer_message.update!(status: Models::Message::STATUS[:failed])
+          outboxer_message.update!(status: Models::Message::Status::FAILED)
 
           outboxer_message.outboxer_exceptions.create!(
             class_name: exception.class.name,
@@ -76,13 +76,13 @@ def republish!(id:)
       ActiveRecord::Base.connection_pool.with_connection do
         outboxer_message = Models::Message.lock.find_by!(id: id)
 
-        if outboxer_message.status != Models::Message::STATUS[:failed]
+        if outboxer_message.status != Models::Message::Status::FAILED
           raise InvalidTransition,
             "cannot transition outboxer message #{id} " \
-            "from #{outboxer_message.status} to #{Models::Message::STATUS[:unpublished]}"
+            "from #{outboxer_message.status} to #{Models::Message::Status::UNPUBLISHED}"
         end
 
-        outboxer_message.update!(status: Models::Message::STATUS[:unpublished])
+        outboxer_message.update!(status: Models::Message::Status::UNPUBLISHED)
 
         outboxer_message
       end
diff --git a/lib/outboxer/models/message.rb b/lib/outboxer/models/message.rb
index 3152589d..7fc5bc6a 100644
--- a/lib/outboxer/models/message.rb
+++ b/lib/outboxer/models/message.rb
@@ -19,17 +19,21 @@ module Models
     class Message < ::ActiveRecord::Base
       self.table_name = :outboxer_messages
 
-      STATUS = {
-        unpublished: "unpublished",
-        publishing: "publishing",
-        failed: "failed"
-      }
+      module Status
+        UNPUBLISHED = 'unpublished'
+        PUBLISHING = 'publishing'
+        PUBLISHED = 'published'
+        FAILED = 'failed'
+      end
 
-      scope :unpublished, -> { where(status: STATUS[:unpublished]) }
-      scope :publishing, -> { where(status: STATUS[:publishing]) }
-      scope :failed, -> { where(status: STATUS[:failed]) }
+      STATUSES = [Status::UNPUBLISHED, Status::PUBLISHING, Status::PUBLISHED, Status::FAILED]
 
-      attribute :status, default: -> { STATUS[:unpublished] }
+      scope :unpublished, -> { where(status: UNPUBLISHED) }
+      scope :publishing, -> { where(status: PUBLISHING) }
+      scope :failed, -> { where(status: FAILED) }
+
+      attribute :status, default: -> { Status::UNPUBLISHED }
+      # validates :status, inclusion: { in: STATUSES }
 
       belongs_to :messageable, polymorphic: true
 
diff --git a/spec/lib/outboxer/message/failed_spec.rb b/spec/lib/outboxer/message/failed_spec.rb
index eff11c89..5eb9e905 100644
--- a/spec/lib/outboxer/message/failed_spec.rb
+++ b/spec/lib/outboxer/message/failed_spec.rb
@@ -10,7 +10,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 1,
-            status: Models::Message::STATUS[:publishing],
+            status: Models::Message::Status::PUBLISHING,
             created_at: DateTime.parse('2024-01-14T00:00:00Z'))
         end
 
@@ -18,13 +18,13 @@ module Outboxer
 
         it 'returns updated message' do
           expect(failed_message.id).to eq(publishing_message.id)
-          expect(failed_message.status).to eq(Models::Message::STATUS[:failed])
+          expect(failed_message.status).to eq(Models::Message::Status::FAILED)
         end
 
         it 'updates publishing message status to failed' do
           publishing_message.reload
 
-          expect(publishing_message.status).to eq(Models::Message::STATUS[:failed])
+          expect(publishing_message.status).to eq(Models::Message::Status::FAILED)
         end
       end
 
@@ -33,7 +33,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 1,
-            status: Models::Message::STATUS[:unpublished],
+            status: Models::Message::Status::UNPUBLISHED,
             created_at: DateTime.parse('2024-01-14T00:00:00Z'))
         end
 
diff --git a/spec/lib/outboxer/message/published_spec.rb b/spec/lib/outboxer/message/published_spec.rb
index 2c1b7ac2..c7d0be33 100644
--- a/spec/lib/outboxer/message/published_spec.rb
+++ b/spec/lib/outboxer/message/published_spec.rb
@@ -8,7 +8,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 1,
-            status: Models::Message::STATUS[:publishing],
+            status: Models::Message::Status::PUBLISHING,
             created_at: DateTime.parse('2024-01-14T00:00:00Z'))
         end
 
@@ -28,7 +28,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 1,
-            status: Models::Message::STATUS[:unpublished],
+            status: Models::Message::Status::UNPUBLISHED,
             created_at: DateTime.parse('2024-01-14T00:00:00Z'))
         end
 
diff --git a/spec/lib/outboxer/message/republish_spec.rb b/spec/lib/outboxer/message/republish_spec.rb
index c626cad1..2e9664c7 100644
--- a/spec/lib/outboxer/message/republish_spec.rb
+++ b/spec/lib/outboxer/message/republish_spec.rb
@@ -8,7 +8,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 1,
-            status: Models::Message::STATUS[:failed],
+            status: Models::Message::Status::FAILED,
             created_at: DateTime.parse('2024-01-14T00:00:00Z'))
         end
 
@@ -16,13 +16,13 @@ module Outboxer
 
         it 'returns unpublished message' do
           expect(unpublished_message.id).to eq(failed_message.id)
-          expect(unpublished_message.status).to eq(Models::Message::STATUS[:unpublished])
+          expect(unpublished_message.status).to eq(Models::Message::Status::UNPUBLISHED)
         end
 
         it 'updates failed message status to unpublishied' do
           failed_message.reload
 
-          expect(failed_message.status).to eq(Models::Message::STATUS[:unpublished])
+          expect(failed_message.status).to eq(Models::Message::Status::UNPUBLISHED)
         end
       end
 
@@ -31,7 +31,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 1,
-            status: Models::Message::STATUS[:unpublished],
+            status: Models::Message::Status::UNPUBLISHED,
             created_at: DateTime.parse('2024-01-14T00:00:00Z'))
         end
 
diff --git a/spec/lib/outboxer/message/unpublished_spec.rb b/spec/lib/outboxer/message/unpublished_spec.rb
index 2f4b46cf..1b879dfb 100644
--- a/spec/lib/outboxer/message/unpublished_spec.rb
+++ b/spec/lib/outboxer/message/unpublished_spec.rb
@@ -9,12 +9,12 @@ module Outboxer
             Models::Message.create!(
               messageable_type: 'DummyType',
               messageable_id: 1,
-              status: Models::Message::STATUS[:unpublished],
+              status: Models::Message::Status::UNPUBLISHED,
               created_at: DateTime.parse('2024-01-14T00:00:00Z')),
             Models::Message.create!(
               messageable_type: 'DummyType',
               messageable_id: 2,
-              status: Models::Message::STATUS[:unpublished],
+              status: Models::Message::Status::UNPUBLISHED,
               created_at: DateTime.parse('2024-01-14T00:00:01Z'))
           ]
         end
@@ -29,11 +29,12 @@ module Outboxer
               publishing_message = publishing_messages.first
               expect(publishing_message.messageable_type).to eq('DummyType')
               expect(publishing_message.messageable_id).to eq(1)
-              expect(publishing_message.status).to eq(Models::Message::STATUS[:publishing])
+              expect(publishing_message.status).to eq(Models::Message::Status::PUBLISHING)
             end
 
             it 'keeps last unpublished message' do
-              remaining_messages = Models::Message.where(status: Models::Message::STATUS[:unpublished])
+              remaining_messages = Models::Message.where(status: Models::Message::Status::UNPUBLISHED)
+
               expect(remaining_messages.count).to eq(1)
 
               remaining_message = remaining_messages.last
@@ -54,7 +55,7 @@ module Outboxer
             end
 
             it 'keeps first unpublished message' do
-              remaining_messages = Models::Message.where(status: Models::Message::STATUS[:unpublished])
+              remaining_messages = Models::Message.where(status: Models::Message::Status::UNPUBLISHED)
               expect(remaining_messages.count).to eq(1)
 
               remaining_message = remaining_messages.first
diff --git a/spec/lib/outboxer/messageable_spec.rb b/spec/lib/outboxer/messageable_spec.rb
index f05a5b17..9e0859e6 100644
--- a/spec/lib/outboxer/messageable_spec.rb
+++ b/spec/lib/outboxer/messageable_spec.rb
@@ -25,7 +25,7 @@ class Event < ActiveRecord::Base
     let(:outboxer_message) { event.outboxer_message }
 
     it 'creates outboxer message' do
-      expect(outboxer_message.status).to eq(Outboxer::Models::Message::STATUS[:unpublished])
+      expect(outboxer_message.status).to eq(Outboxer::Models::Message::Status::UNPUBLISHED)
       expect(outboxer_message.messageable_type).to eq(event.class.to_s)
       expect(outboxer_message.messageable_id).to eq(event.id)
       expect(outboxer_message.created_at).to be_present
diff --git a/spec/lib/outboxer/publisher/pop_message_spec.rb b/spec/lib/outboxer/publisher/pop_message_spec.rb
index 500ee138..e8242515 100644
--- a/spec/lib/outboxer/publisher/pop_message_spec.rb
+++ b/spec/lib/outboxer/publisher/pop_message_spec.rb
@@ -11,7 +11,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 1,
-            status: Models::Message::STATUS[:publishing])
+            status: Models::Message::Status::PUBLISHING)
         end
 
         before do
@@ -40,7 +40,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 1,
-            status: 'publishing')
+            status: Models::Message::Status::PUBLISHING)
         end
 
         let(:error) { StandardError.new('processing error') }
@@ -68,7 +68,7 @@ module Outboxer
           end
 
           updated_message = Models::Message.find(message.id)
-          expect(updated_message.status).to eq(Models::Message::STATUS[:failed])
+          expect(updated_message.status).to eq(Models::Message::Status::FAILED)
           expect(updated_message.outboxer_exceptions.count).to eq(1)
           expect(updated_message.outboxer_exceptions.first.class_name).to eq(error.class.name)
           expect(updated_message.outboxer_exceptions.first.message_text).to eq(error.message)
diff --git a/spec/lib/outboxer/publisher/publish_spec.rb b/spec/lib/outboxer/publisher/publish_spec.rb
index 259eee02..cb782c74 100644
--- a/spec/lib/outboxer/publisher/publish_spec.rb
+++ b/spec/lib/outboxer/publisher/publish_spec.rb
@@ -17,7 +17,7 @@ module Outboxer
         Models::Message.create!(
           messageable_type: 'DummyType',
           messageable_id: 1,
-          status: Models::Message::STATUS[:unpublished])
+          status: Models::Message::Status::UNPUBLISHED)
       end
 
       context 'when message published successfully' do
@@ -31,7 +31,7 @@ module Outboxer
           ) do |publishing_message|
             expect(publishing_message.messageable_type).to eq('DummyType')
             expect(publishing_message.messageable_id).to eq(1)
-            expect(publishing_message.status).to eq(Models::Message::STATUS[:publishing])
+            expect(publishing_message.status).to eq(Models::Message::Status::PUBLISHING)
 
             Publisher.stop!
           end
diff --git a/spec/lib/outboxer/publisher/push_messages_spec.rb b/spec/lib/outboxer/publisher/push_messages_spec.rb
index 6e19a2ed..e49fc964 100644
--- a/spec/lib/outboxer/publisher/push_messages_spec.rb
+++ b/spec/lib/outboxer/publisher/push_messages_spec.rb
@@ -15,7 +15,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 2,
-            status: Models::Message::STATUS[:unpublished])
+            status: Models::Message::Status::UNPUBLISHED)
         end
 
         before do
@@ -74,7 +74,7 @@ module Outboxer
           Models::Message.create!(
             messageable_type: 'DummyType',
             messageable_id: 1,
-            status: Models::Message::STATUS[:publishing])
+            status: Models::Message::Status::PUBLISHING)
         end
 
         before do