diff --git a/app/models/account.rb b/app/models/account.rb
index 5fa1f0cebf6..6ae05f330b9 100644
--- a/app/models/account.rb
+++ b/app/models/account.rb
@@ -69,6 +69,7 @@ class Account < ApplicationRecord
   STALE_THRESHOLD = 1.day
   DEFAULT_FIELDS_SIZE = 4
   INSTANCE_ACTOR_ID = -99
+  INSTANCE_ACTOR_USERNAME = 'mastodon.internal'
 
   USERNAME_RE   = /[a-z0-9_]+([.-]+[a-z0-9_]+)*/i
   MENTION_RE    = %r{(?<![=/[:word:]])@((#{USERNAME_RE})(?:@[[:word:]]+([.-]+[[:word:]]+)*)?)}
diff --git a/app/models/concerns/account/finder_concern.rb b/app/models/concerns/account/finder_concern.rb
index 249a7b5fd17..02784dc94f3 100644
--- a/app/models/concerns/account/finder_concern.rb
+++ b/app/models/concerns/account/finder_concern.rb
@@ -13,11 +13,12 @@ module Account::FinderConcern
     end
 
     def representative
-      actor = Account.find(Account::INSTANCE_ACTOR_ID).tap(&:ensure_keys!)
-      actor.update!(username: 'mastodon.internal') if actor.username.include?(':')
-      actor
+      Account.find(Account::INSTANCE_ACTOR_ID).tap do |actor|
+        actor.ensure_keys!
+        actor.update!(username: Account::INSTANCE_ACTOR_USERNAME) if actor.username.include?(':')
+      end
     rescue ActiveRecord::RecordNotFound
-      Account.create!(id: Account::INSTANCE_ACTOR_ID, actor_type: 'Application', locked: true, username: 'mastodon.internal')
+      Account.create!(id: Account::INSTANCE_ACTOR_ID, actor_type: 'Application', locked: true, username: Account::INSTANCE_ACTOR_USERNAME)
     end
 
     def find_local(username)
diff --git a/db/seeds/02_instance_actor.rb b/db/seeds/02_instance_actor.rb
index 2b6befec0d9..74810e4f48c 100644
--- a/db/seeds/02_instance_actor.rb
+++ b/db/seeds/02_instance_actor.rb
@@ -1,3 +1,3 @@
 # frozen_string_literal: true
 
-Account.create_with(actor_type: 'Application', locked: true, username: 'mastodon.internal').find_or_create_by(id: Account::INSTANCE_ACTOR_ID)
+Account.create_with(actor_type: 'Application', locked: true, username: Account::INSTANCE_ACTOR_USERNAME).find_or_create_by(id: Account::INSTANCE_ACTOR_ID)
diff --git a/spec/models/concerns/account/finder_concern_spec.rb b/spec/models/concerns/account/finder_concern_spec.rb
index b3fae56dfc5..dba834812c4 100644
--- a/spec/models/concerns/account/finder_concern_spec.rb
+++ b/spec/models/concerns/account/finder_concern_spec.rb
@@ -3,6 +3,37 @@
 require 'rails_helper'
 
 RSpec.describe Account::FinderConcern do
+  describe '.representative' do
+    context 'with an instance actor using an invalid legacy username' do
+      let(:legacy_value) { 'legacy:value' }
+
+      before { Account.find(Account::INSTANCE_ACTOR_ID).update_attribute(:username, legacy_value) }
+
+      it 'updates the username to the new value' do
+        expect { Account.representative }
+          .to change { Account.find(Account::INSTANCE_ACTOR_ID).username }.from(legacy_value).to(Account::INSTANCE_ACTOR_USERNAME)
+      end
+    end
+
+    context 'without an instance actor' do
+      before { Account.find(Account::INSTANCE_ACTOR_ID).destroy! }
+
+      it 'creates an instance actor' do
+        expect { Account.representative }
+          .to change(Account.where(id: Account::INSTANCE_ACTOR_ID), :count).from(0).to(1)
+      end
+    end
+
+    context 'with a correctly loaded instance actor' do
+      let(:instance_actor) { Account.find(Account::INSTANCE_ACTOR_ID) }
+
+      it 'returns the instance actor record' do
+        expect(Account.representative)
+          .to eq(instance_actor)
+      end
+    end
+  end
+
   describe 'local finders' do
     let!(:account) { Fabricate(:account, username: 'Alice') }
 
diff --git a/spec/requests/instance_actor_spec.rb b/spec/requests/instance_actor_spec.rb
index ce0bbe3b820..4023cc85c14 100644
--- a/spec/requests/instance_actor_spec.rb
+++ b/spec/requests/instance_actor_spec.rb
@@ -19,7 +19,7 @@ RSpec.describe 'Instance actor endpoint' do
           .to include(
             id: instance_actor_url,
             type: 'Application',
-            preferredUsername: 'mastodon.internal',
+            preferredUsername: Account::INSTANCE_ACTOR_USERNAME,
             inbox: instance_actor_inbox_url,
             outbox: instance_actor_outbox_url,
             publicKey: include(