Nested Rollbacks not working (guessing its a sqlite thing)

sad_panda.rb

require 'active_record'
ActiveRecord::Base.establish_connection adapter: 'sqlite3', database: ':memory:'

ActiveRecord::Schema.define do
  self.verbose = false
  create_table :users
end

User = Class.new ActiveRecord::Base

def create_user_then_raise_error_in_transaction
  User.transaction do
    User.create
    raise
  end
rescue
end

# a single transaction rolls it back
create_user_then_raise_error_in_transaction
User.count # => 0

# nested transactions do not work
User.transaction { create_user_then_raise_error_in_transaction }
User.count # => 1


# for reaaaaaalz >.<
create_user_then_raise_error_in_transaction
create_user_then_raise_error_in_transaction
create_user_then_raise_error_in_transaction
create_user_then_raise_error_in_transaction
create_user_then_raise_error_in_transaction
create_user_then_raise_error_in_transaction
User.count # => 1
User.transaction { create_user_then_raise_error_in_transaction  }
User.count # => 2

Apparently the solution is to use requires_new: true, IDK why.