diff --git a/lib/generators/outboxable/install_generator.rb b/lib/generators/outboxable/install_generator.rb
index caa3062..d1a7c09 100644
--- a/lib/generators/outboxable/install_generator.rb
+++ b/lib/generators/outboxable/install_generator.rb
@@ -5,8 +5,8 @@ class InstallGenerator < Rails::Generators::Base
     source_root File.expand_path('../../templates', __dir__)
     class_option :orm, type: :string, default: 'activerecord'
 
-    def initialize
-      super
+    def initialize(*args)
+      super(*args)
 
       @orm = options[:orm] || 'activerecord'
       %w[activerecord mongoid].include?(@orm) || raise(ArgumentError, 'Invalid ORM. Only ActiveRecord and Mongoid are supported.')
diff --git a/lib/outboxable/rabbitmq/publisher.rb b/lib/outboxable/rabbitmq/publisher.rb
index 034d1e5..1770881 100644
--- a/lib/outboxable/rabbitmq/publisher.rb
+++ b/lib/outboxable/rabbitmq/publisher.rb
@@ -20,7 +20,12 @@ def publish
           exchange = channel.topic(@resource.exchange, durable: true)
 
           # Publish the CloudEvent resource to the exchange
-          exchange.publish(to_envelope(resource: @resource), routing_key: @resource.routing_key, headers: @resource.try(:headers) || {})
+          exchange.publish(
+            to_envelope(resource: @resource),
+            routing_key: @resource.routing_key,
+            headers: @resource.try(:headers) || {},
+            content_type: @resource.try(:content_type) || 'application/json'
+          )
 
           # Wait for confirmation
           confirmed = channel.wait_for_confirms
diff --git a/lib/templates/create_outboxable_outboxes.rb b/lib/templates/create_outboxable_outboxes.rb
index 800acdb..02a6e7b 100644
--- a/lib/templates/create_outboxable_outboxes.rb
+++ b/lib/templates/create_outboxable_outboxes.rb
@@ -7,6 +7,7 @@ def change
 
       t.string :exchange, null: false, default: ''
       t.string :routing_key, null: false, default: ''
+      t.string :content_type, null: false, default: 'application/json'
 
       t.integer  :attempts, null: false, default: 0
       t.datetime :last_attempted_at, null: true
@@ -21,5 +22,7 @@ def change
 
       t.timestamps
     end
+
+    add_index :outboxes, %i[status last_attempted_at], name: 'index_outboxes_on_outboxable_status_and_last_attempted_at'
   end
 end
diff --git a/lib/templates/mongoid_outbox.rb b/lib/templates/mongoid_outbox.rb
index f905c51..cbe3dd7 100644
--- a/lib/templates/mongoid_outbox.rb
+++ b/lib/templates/mongoid_outbox.rb
@@ -10,6 +10,7 @@ class Outbox
 
   field :exchange, type: String, default: ''
   field :routing_key, type: String, default: ''
+  field :content_type, type: String, default: 'application/json'
 
   field :attempts, type: Integer, default: 0