diff --git a/core/cmdbsource.class.inc.php b/core/cmdbsource.class.inc.php
index 1f71e33d96..6d2eae7bb3 100644
--- a/core/cmdbsource.class.inc.php
+++ b/core/cmdbsource.class.inc.php
@@ -68,6 +68,7 @@ class CMDBSource
 
 	/** @var mysqli $m_oMysqli */
 	protected static $m_oMysqli;
+	/** @var mysqli or mock used for test purpose, only used in query() method */
 	protected static $oMySQLiForQuery;
 
 	/**