diff --git a/core/DbConnectionWrapper.php b/core/DbConnectionWrapper.php
index f432bb262..5de337513 100644
--- a/core/DbConnectionWrapper.php
+++ b/core/DbConnectionWrapper.php
@@ -60,6 +60,7 @@ class DbConnectionWrapper
 	 *
 	 * @param \mysqli|null $oMysqli
 	 * @since 3.0.4 3.1.1 3.2.0 Param $oMysqli becomes nullable
+	 * @since 3.1.0-4 N°6848 backport of restoring cnx on null parameter value
 	 */
 	public static function SetDbConnectionMockForQuery(?mysqli $oMysqli = null): void
 	{
diff --git a/tests/php-unit-tests/unitary-tests/core/CMDBSource/TransactionsTest.php b/tests/php-unit-tests/unitary-tests/core/CMDBSource/TransactionsTest.php
index 44482827d..1afbe1260 100644
--- a/tests/php-unit-tests/unitary-tests/core/CMDBSource/TransactionsTest.php
+++ b/tests/php-unit-tests/unitary-tests/core/CMDBSource/TransactionsTest.php
@@ -280,7 +280,7 @@ class TransactionsTest extends ItopTestCase
 	protected function tearDown(): void
 	{
 		try {
-			DbConnectionWrapper::SetDbConnectionMockForQuery();
+			DbConnectionWrapper::SetDbConnectionMockForQuery(); // Else will throw error on PHP 8.1+ (see N°6848)
 			parent::tearDown();
 		}
 		catch (MySQLTransactionNotClosedException $e) {