diff --git a/app/lib/activitypub/activity/create.rb b/app/lib/activitypub/activity/create.rb
index a6f1e60d9..081e80570 100644
--- a/app/lib/activitypub/activity/create.rb
+++ b/app/lib/activitypub/activity/create.rb
@@ -26,7 +26,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
 
   def find_existing_status
     status   = status_from_uri(object_uri)
-    status ||= Status.find_by(uri: @object['_:atomUri']) if @object['_:atomUri'].present?
+    status ||= Status.find_by(uri: @object['atomUri']) if @object['atomUri'].present?
     status
   end
 
@@ -43,7 +43,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
       sensitive: @object['sensitive'] || false,
       visibility: visibility_from_audience,
       thread: replied_to_status,
-      conversation: conversation_from_uri(@object['_:conversation']),
+      conversation: conversation_from_uri(@object['conversation']),
     }
   end
 
@@ -125,7 +125,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
       @replied_to_status = nil
     else
       @replied_to_status   = status_from_uri(in_reply_to_uri)
-      @replied_to_status ||= status_from_uri(@object['_:inReplyToAtomUri']) if @object['_:inReplyToAtomUri'].present?
+      @replied_to_status ||= status_from_uri(@object['inReplyToAtomUri']) if @object['inReplyToAtomUri'].present?
       @replied_to_status
     end
   end
diff --git a/app/lib/activitypub/activity/delete.rb b/app/lib/activitypub/activity/delete.rb
index 9d804c86d..4c6afb090 100644
--- a/app/lib/activitypub/activity/delete.rb
+++ b/app/lib/activitypub/activity/delete.rb
@@ -17,7 +17,7 @@ class ActivityPub::Activity::Delete < ActivityPub::Activity
 
   def delete_note
     status   = Status.find_by(uri: object_uri, account: @account)
-    status ||= Status.find_by(uri: @object['_:atomUri'], account: @account) if @object.is_a?(Hash) && @object['_:atomUri'].present?
+    status ||= Status.find_by(uri: @object['atomUri'], account: @account) if @object.is_a?(Hash) && @object['atomUri'].present?
 
     delete_later!(object_uri)
 
diff --git a/app/lib/activitypub/adapter.rb b/app/lib/activitypub/adapter.rb
index 92210579e..fe4dddd38 100644
--- a/app/lib/activitypub/adapter.rb
+++ b/app/lib/activitypub/adapter.rb
@@ -1,6 +1,24 @@
 # frozen_string_literal: true
 
 class ActivityPub::Adapter < ActiveModelSerializers::Adapter::Base
+  CONTEXT = {
+    '@context': [
+      'https://www.w3.org/ns/activitystreams',
+      'https://w3id.org/security/v1',
+
+      {
+        'locked'    => 'as:locked',
+        'sensitive' => 'as:sensitive',
+        'Hashtag'   => 'as:Hashtag',
+
+        'ostatus'          => 'http://ostatus.org#',
+        'atomUri'          => 'ostatus:atomUri',
+        'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri',
+        'conversation'     => 'ostatus:conversation',
+      },
+    ],
+  }.freeze
+
   def self.default_key_transform
     :camel_lower
   end
@@ -11,7 +29,7 @@ class ActivityPub::Adapter < ActiveModelSerializers::Adapter::Base
 
   def serializable_hash(options = nil)
     options = serialization_options(options)
-    serialized_hash = { '@context': [ActivityPub::TagManager::CONTEXT, 'https://w3id.org/security/v1'] }.merge(ActiveModelSerializers::Adapter::Attributes.new(serializer, instance_options).serializable_hash(options))
+    serialized_hash = CONTEXT.merge(ActiveModelSerializers::Adapter::Attributes.new(serializer, instance_options).serializable_hash(options))
     self.class.transform_key_casing!(serialized_hash, instance_options)
   end
 end
diff --git a/app/serializers/activitypub/actor_serializer.rb b/app/serializers/activitypub/actor_serializer.rb
index a72ecee24..f004dc326 100644
--- a/app/serializers/activitypub/actor_serializer.rb
+++ b/app/serializers/activitypub/actor_serializer.rb
@@ -6,12 +6,10 @@ class ActivityPub::ActorSerializer < ActiveModel::Serializer
   attributes :id, :type, :following, :followers,
              :inbox, :outbox, :shared_inbox,
              :preferred_username, :name, :summary,
-             :url
+             :url, :locked
 
   has_one :public_key, serializer: ActivityPub::PublicKeySerializer
 
-  attribute :locked, key: '_:locked'
-
   class ImageSerializer < ActiveModel::Serializer
     include RoutingHelper
 
diff --git a/app/serializers/activitypub/delete_serializer.rb b/app/serializers/activitypub/delete_serializer.rb
index a041c577b..87a43b95d 100644
--- a/app/serializers/activitypub/delete_serializer.rb
+++ b/app/serializers/activitypub/delete_serializer.rb
@@ -2,8 +2,7 @@
 
 class ActivityPub::DeleteSerializer < ActiveModel::Serializer
   class TombstoneSerializer < ActiveModel::Serializer
-    attributes :id, :type
-    attribute :atom_uri, key: '_:atomUri'
+    attributes :id, :type, :atom_uri
 
     def id
       ActivityPub::TagManager.instance.uri_for(object)
diff --git a/app/serializers/activitypub/note_serializer.rb b/app/serializers/activitypub/note_serializer.rb
index 15031dfdc..d42f54263 100644
--- a/app/serializers/activitypub/note_serializer.rb
+++ b/app/serializers/activitypub/note_serializer.rb
@@ -3,14 +3,13 @@
 class ActivityPub::NoteSerializer < ActiveModel::Serializer
   attributes :id, :type, :summary, :content,
              :in_reply_to, :published, :url,
-             :attributed_to, :to, :cc, :sensitive
+             :attributed_to, :to, :cc, :sensitive,
+             :atom_uri, :in_reply_to_atom_uri,
+             :conversation
 
   has_many :media_attachments, key: :attachment
   has_many :virtual_tags, key: :tag
 
-  attribute :atom_uri, key: '_:atomUri', if: :local?
-  attribute :in_reply_to_atom_uri, key: '_:inReplyToAtomUri'
-
   def id
     ActivityPub::TagManager.instance.uri_for(object)
   end
@@ -62,6 +61,8 @@ class ActivityPub::NoteSerializer < ActiveModel::Serializer
   end
 
   def atom_uri
+    return unless object.local?
+
     ::TagManager.instance.uri_for(object)
   end
 
@@ -71,6 +72,14 @@ class ActivityPub::NoteSerializer < ActiveModel::Serializer
     ::TagManager.instance.uri_for(object.thread)
   end
 
+  def conversation
+    if object.conversation.uri?
+      object.conversation.uri
+    else
+      TagManager.instance.unique_tag(object.conversation.created_at, object.conversation.id, 'Conversation')
+    end
+  end
+
   def local?
     object.account.local?
   end
diff --git a/app/services/activitypub/fetch_remote_status_service.rb b/app/services/activitypub/fetch_remote_status_service.rb
index c114515cd..68ca58d62 100644
--- a/app/services/activitypub/fetch_remote_status_service.rb
+++ b/app/services/activitypub/fetch_remote_status_service.rb
@@ -25,8 +25,8 @@ class ActivityPub::FetchRemoteStatusService < BaseService
   def activity_json
     if %w(Note Article).include? @json['type']
       {
-        'type' => 'Create',
-        'actor' => first_of_value(@json['attributedTo']),
+        'type'   => 'Create',
+        'actor'  => first_of_value(@json['attributedTo']),
         'object' => @json,
       }
     else
diff --git a/app/services/activitypub/process_account_service.rb b/app/services/activitypub/process_account_service.rb
index 99f9dbdc2..44798d051 100644
--- a/app/services/activitypub/process_account_service.rb
+++ b/app/services/activitypub/process_account_service.rb
@@ -50,7 +50,7 @@ class ActivityPub::ProcessAccountService < BaseService
     @account.avatar_remote_url   = image_url('icon')
     @account.header_remote_url   = image_url('image')
     @account.public_key          = public_key || ''
-    @account.locked              = @json['_:locked'] || false
+    @account.locked              = @json['locked'] || false
     @account.save!
   end