FuelPHPのcoreのerrorhandler.phpがErrorhandlerを継承していない？

未だにこれの謎が解けぬ……なんなのだろう？ ネームスペースの問題だとは思うが……

PHP Fatal error:  Uncaught Exception: File "COREPATH/classes/errorhandler.php" does not contain class "Fuel\Core\Errorhandler" in /hoge/fuel/core/classes/autoloader.php:397
Stack trace:
#0 /hoge/fuel/core/classes/autoloader.php(236): Fuel\Core\Autoloader::init_class('Fuel\\Core\\Error...', '/vagrant_data/i...')
#1 [internal function]: Fuel\Core\Autoloader::load('Fuel\\Core\\Error...')
#2 [internal function]: spl_autoload_call('Fuel\\Core\\Error...')
#3 /hoge/fuel/core/classes/autoloader.php(247): class_alias('Fuel\\Core\\Error...', 'Errorhandler')
#4 [internal function]: Fuel\Core\Autoloader::load('Errorhandler')
#5 /hoge/fuel/core/bootstrap.php(71): spl_autoload_call('Errorhandler')
#6 [internal function]: PHPUnit_Util_Fileloader::{closure}()
#7 {main}
  thrown in /hoge/fuel/core/classes/autoloader.php on line 397
PHP Stack trace:
PHP   1. {main}() /usr/local/bin/phpunit:0
PHP   2. PHPUnit_TextUI_Command::main() /usr/local/bin/phpunit:583
PHP   3. PHPUnit_TextUI_Command->run() phar:///usr/local/bin/phpunit/phpunit/TextUI/Command.php:118
PHP   4. PHPUnit_TextUI_TestRunner->doRun() phar:///usr/local/bin/phpunit/phpunit/TextUI/Command.php:188

Fatal error: Uncaught Exception: File "COREPATH/classes/errorhandler.php" does not contain class "Fuel\Core\Errorhandler" in /hoge/fuel/core/classes/autoloader.php on line 397

Call Stack:
    0.0009     495536   1. {main}() /usr/local/bin/phpunit:0
    0.2010   10224488   2. PHPUnit_TextUI_Command::main() /usr/local/bin/phpunit:583
    0.2010   10227648   3. PHPUnit_TextUI_Command->run() phar:///usr/local/bin/phpunit/phpunit/TextUI/Command.php:118
    1.4838   14664928   4. PHPUnit_TextUI_TestRunner->doRun() phar:///usr/local/bin/phpunit/phpunit/TextUI/Command.php:188

Exception: File "COREPATH/classes/errorhandler.php" does not contain class "Fuel\Core\Errorhandler" in /hoge/fuel/core/classes/autoloader.php on line 397

Call Stack:
    0.0009     495536   1. {main}() /usr/local/bin/phpunit:0
    0.2010   10224488   2. PHPUnit_TextUI_Command::main() /usr/local/bin/phpunit:583
    0.2010   10227648   3. PHPUnit_TextUI_Command->run() phar:///usr/local/bin/phpunit/phpunit/TextUI/Command.php:118
    1.4838   14664928   4. PHPUnit_TextUI_TestRunner->doRun() phar:///usr/local/bin/phpunit/phpunit/TextUI/Command.php:188
   86.1126   41742880   5. PHPUnit_Util_Fileloader::{closure:/hoge/fuel/core/bootstrap.php:34-72}() /hoge/fuel/core/bootstrap.php:0
   86.1129   41743200   6. spl_autoload_call() /hoge/fuel/core/bootstrap.php:71
   86.1129   41743240   7. Fuel\Core\Autoloader::load() /hoge/fuel/core/bootstrap.php:71
   86.1153   41743440   8. class_alias() /hoge/fuel/core/classes/autoloader.php:247
   86.1154   41743488   9. spl_autoload_call() /hoge/fuel/core/classes/autoloader.php:247
   86.1154   41743536  10. Fuel\Core\Autoloader::load() /hoge/fuel/core/classes/autoloader.php:247
   86.1154   41743632  11. Fuel\Core\Autoloader::init_class() /hoge/fuel/core/classes/autoloader.php:236