diff --git a/app/serializers/rest/instance_serializer.rb b/app/serializers/rest/instance_serializer.rb
index 5ae1099d0..c9c76c700 100644
--- a/app/serializers/rest/instance_serializer.rb
+++ b/app/serializers/rest/instance_serializer.rb
@@ -11,11 +11,16 @@ class REST::InstanceSerializer < ActiveModel::Serializer
 
   attributes :domain, :title, :version, :source_url, :description,
              :usage, :thumbnail, :languages, :configuration,
+             :max_toot_chars,
              :registrations
 
   has_one :contact, serializer: ContactSerializer
   has_many :rules, serializer: REST::RuleSerializer
 
+  def max_toot_chars
+    StatusLengthValidator::MAX_CHARS
+  end
+
   def thumbnail
     if object.thumbnail
       {