diff --git a/tests/php-unit-tests/unitary-tests/setup/unattended-install/InstallationFileServiceTest.php b/tests/php-unit-tests/unitary-tests/setup/unattended-install/InstallationFileServiceTest.php
index b47dd00d1..c872c3ed7 100644
--- a/tests/php-unit-tests/unitary-tests/setup/unattended-install/InstallationFileServiceTest.php
+++ b/tests/php-unit-tests/unitary-tests/setup/unattended-install/InstallationFileServiceTest.php
@@ -5,6 +5,8 @@ namespace Combodo\iTop\Test\UnitTest\Setup\UnattendedInstall;
 use PHPUnit\Framework\TestCase;
 
 class InstallationFileServiceTest extends TestCase {
+	private $sFolderToCleanup;
+
 	protected function setUp(): void {
 		parent::setUp();
 		require_once(dirname(__FILE__, 6) . '/setup/unattended-install/InstallationFileService.php');