[Flow] Failed to compile PHP files in directory next to Domain directory

[Rocky]

Hi,

I created folder Utility in FlowDir/Packages/Application/Mycompany.Package/Class/Mycompany/Package/. In the Utility folder I had Debug.php which reads likes below
<?php
namespace Mycompany\Package\Unitlity;

use TYPO3\Flow\Annotations as Flow;
Class Debug {
 // My code here
 static public function CuoWu() {
 }
}

In one of my Controller files, I have below code:
\Mycompany\Package\Utility::CuoWu();

But I get fatal error saying: "PHP Fatal error:  Class 'Mycompany\\Package\\Utility\\Debug_Original' not found in /vagrant/Typo3Flow/Data/Temporary/Development/Cache/Code/Flow_Object_Classes/Mycompany_Package_Utility_Debug.php on line 34". The problem is gone if I edit the Mycompany_Package_Utility_Debug.php by adding _Original to the class name. What configuration I need to make to make the class compile right please?