diff --git a/lib/Query/DataQuery.php b/lib/Query/DataQuery.php
index ea33803..4203182 100644
--- a/lib/Query/DataQuery.php
+++ b/lib/Query/DataQuery.php
@@ -4,6 +4,8 @@
  *
  * @copyright 2021 Marcin Łojewski <dev@mlojewski.me>
  * @author    Marcin Łojewski <dev@mlojewski.me>
+ * @copyright 2025 Claus-Justus Heine
+ * @author    Claus-Justus Heine <himself@claus-justus-heine.de>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
@@ -21,6 +23,8 @@
 
 namespace OCA\UserSQL\Query;
 
+use UnexpectedValueException;
+
 use Doctrine\DBAL\Driver\Statement;
 use Doctrine\DBAL\Exception as DBALException;
 use OC\DB\Connection;
@@ -151,6 +155,10 @@ class DataQuery
             "driverOptions" => array()
         );
 
+        if (empty($this->properties[DB::DRIVER])) {
+          throw new UnexpectedValueException('Attempt to connect without configuration.');
+        }
+
         if ($this->properties[DB::DRIVER] == 'mysql') {
             if ($this->properties[DB::SSL_CA]) {
                 $parameters["driverOptions"][\PDO::MYSQL_ATTR_SSL_CA] = \OC::$SERVERROOT . '/' . $this->properties[DB::SSL_CA];