diff --git a/Classes/Command/SequenceCommandController.php b/Classes/Command/SequenceCommandController.php
index ce884f8..cf9dc7e 100644
--- a/Classes/Command/SequenceCommandController.php
+++ b/Classes/Command/SequenceCommandController.php
@@ -5,7 +5,10 @@ declare(strict_types=1);
 namespace DigiComp\Sequence\Command;
 
 use DigiComp\Sequence\Domain\Model\Insert;
+use DigiComp\Sequence\Service\Exception as DigiCompSequenceServiceException;
 use DigiComp\Sequence\Service\SequenceGenerator;
+use Doctrine\DBAL\Driver\Exception as DoctrineDBALDriverException;
+use Doctrine\DBAL\Exception as DoctrineDBALException;
 use Doctrine\ORM\EntityManagerInterface;
 use Neos\Flow\Annotations as Flow;
 use Neos\Flow\Cli\CommandController;
@@ -34,6 +37,7 @@ class SequenceCommandController extends CommandController
      *
      * @param int $to
      * @param string $type
+     * @throws DigiCompSequenceServiceException
      */
     public function advanceCommand(int $to, string $type): void
     {
@@ -42,6 +46,9 @@ class SequenceCommandController extends CommandController
 
     /**
      * @param string[] $typesToClean
+     * @throws DigiCompSequenceServiceException
+     * @throws DoctrineDBALDriverException
+     * @throws DoctrineDBALException
      */
     public function cleanSequenceInsertsCommand(array $typesToClean = [])
     {
diff --git a/Classes/Service/SequenceGenerator.php b/Classes/Service/SequenceGenerator.php
index d9a3399..7c7b744 100644
--- a/Classes/Service/SequenceGenerator.php
+++ b/Classes/Service/SequenceGenerator.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace DigiComp\Sequence\Service;
 
 use DigiComp\Sequence\Domain\Model\Insert;
+use Doctrine\DBAL\Driver\Exception as DoctrineDBALDriverException;
 use Doctrine\DBAL\Exception as DoctrineDBALException;
 use Doctrine\ORM\EntityManagerInterface;
 use Neos\Flow\Annotations as Flow;
@@ -37,6 +38,7 @@ class SequenceGenerator
      * @param string|object $type
      * @return int
      * @throws Exception
+     * @throws DoctrineDBALDriverException
      * @throws DoctrineDBALException
      */
     public function getNextNumberFor($type): int
@@ -71,10 +73,10 @@ class SequenceGenerator
             return false;
         } catch (DoctrineDBALException $e) {
             if (!$e->getPrevious() instanceof \PDOException) {
-                $this->logger->critical('Exception occured: ' . $e->getMessage());
+                $this->logger->critical('Exception occurred: ' . $e->getMessage());
             }
         } catch (\Exception $e) {
-            $this->logger->critical('Exception occured: ' . $e->getMessage());
+            $this->logger->critical('Exception occurred: ' . $e->getMessage());
         }
 
         return false;
@@ -98,6 +100,7 @@ class SequenceGenerator
      * @param string|object $type
      * @return int
      * @throws Exception
+     * @throws DoctrineDBALDriverException
      * @throws DoctrineDBALException
      */
     public function getLastNumberFor($type): int
@@ -107,7 +110,7 @@ class SequenceGenerator
             . $this->entityManager->getClassMetadata(Insert::class)->getTableName()
             . ' WHERE type = :type',
             ['type' => $this->inferTypeFromSource($type)]
-        )->fetchAll(\PDO::FETCH_COLUMN)[0];
+        )->fetchOne();
     }
 
     /**
diff --git a/Tests/Functional/SequenceTest.php b/Tests/Functional/SequenceTest.php
index 7913837..b400c34 100644
--- a/Tests/Functional/SequenceTest.php
+++ b/Tests/Functional/SequenceTest.php
@@ -2,18 +2,24 @@
 
 namespace DigiComp\Sequence\Tests\Functional;
 
+use DigiComp\Sequence\Service\Exception as DigiCompSequenceServiceException;
 use DigiComp\Sequence\Service\SequenceGenerator;
+use Doctrine\DBAL\Driver\Exception as DoctrineDBALDriverException;
+use Doctrine\DBAL\Exception as DoctrineDBALException;
 use Neos\Flow\Tests\FunctionalTestCase;
 
 class SequenceTest extends FunctionalTestCase
 {
     /**
-     * @var bool
+     * @inheritDoc
      */
     protected static $testablePersistenceEnabled = true;
 
     /**
      * @test
+     * @throws DigiCompSequenceServiceException
+     * @throws DoctrineDBALDriverException
+     * @throws DoctrineDBALException
      */
     public function sequenceTest()
     {
@@ -47,6 +53,9 @@ class SequenceTest extends FunctionalTestCase
 
     /**
      * @test
+     * @throws DigiCompSequenceServiceException
+     * @throws DoctrineDBALDriverException
+     * @throws DoctrineDBALException
      */
     public function advanceTest()
     {
diff --git a/composer.json b/composer.json
index b77183f..cace62e 100644
--- a/composer.json
+++ b/composer.json
@@ -3,6 +3,7 @@
     "description": "Sequence is a very simple database agnostic but database based sequence generator",
     "type": "neos-package",
     "require": {
+        "ext-pdo": "*",
         "neos/flow": "^5.3.0 || ^6.3.5",
         "php": "~7.4.0"
     },