embed_in_root works even if serializer is invoked through another serializers' association which itself does not have embed_in_root set

test/fixtures/poro.rb

@@ -22,9 +22,22 @@ class User < Model
   end
 end
 
+class UserInfo < Model
+  def user
+    @user ||= User.new(name: 'N1', email: 'E1')
+  end
+end
+
 class Profile < Model
 end
 
+class Category < Model
+  def posts
+    @posts ||= [Post.new(title: 'T1', body: 'B1'),
+                Post.new(title: 'T2', body: 'B2')]
+  end
+end
+
 class Post < Model
   def comments
     @comments ||= [Comment.new(content: 'C1'),
@@ -47,6 +60,10 @@ class UserSerializer < ActiveModel::Serializer
   has_one :profile
 end
 
+class UserInfoSerializer < ActiveModel::Serializer
+  has_one :user
+end
+
 class ProfileSerializer < ActiveModel::Serializer
   def description
     description = object.read_attribute_for_serialization(:description)
@@ -56,6 +73,12 @@ class ProfileSerializer < ActiveModel::Serializer
   attributes :name, :description
 end
 
+class CategorySerializer < ActiveModel::Serializer
+  attributes :name
+
+  has_many :posts
+end
+
 class PostSerializer < ActiveModel::Serializer
   attributes :title, :body