diff --git a/tests/dbal/write_sequence_test.php b/tests/dbal/write_sequence_test.php
index 8975cfbfb1..f382a971a5 100644
--- a/tests/dbal/write_sequence_test.php
+++ b/tests/dbal/write_sequence_test.php
@@ -33,6 +33,10 @@ class phpbb_dbal_write_sequence_test extends phpbb_database_test_case
 	{
 		$db = $this->new_dbal();
 
+		// dbal uses cache
+		global $cache;
+		$cache = new phpbb_mock_cache();
+
 		$sql = 'INSERT INTO phpbb_users ' . $db->sql_build_array('INSERT', array(
 			'username'			=> $username,
 			'username_clean'	=> $username,