diff --git a/src/Entity/Task.php b/src/Entity/Task.php
index d6793f1..292ba1a 100644
--- a/src/Entity/Task.php
+++ b/src/Entity/Task.php
@@ -52,7 +52,7 @@ public function getInterval()
     /**
      * {@inheritdoc}
      */
-    public function setInterval(CronExpression $interval, \DateTimeImmutable $firstExecution = null, \DateTimeImmutable $lastExecution = null)
+    public function setInterval(CronExpression $interval, ?\DateTimeImmutable $firstExecution = null, ?\DateTimeImmutable $lastExecution = null)
     {
         parent::setInterval($interval, $firstExecution, $lastExecution);
 
diff --git a/src/Entity/TaskExecutionRepository.php b/src/Entity/TaskExecutionRepository.php
index 7236008..430d154 100644
--- a/src/Entity/TaskExecutionRepository.php
+++ b/src/Entity/TaskExecutionRepository.php
@@ -129,7 +129,7 @@ public function findByTaskUuid($taskUuid)
     /**
      * {@inheritdoc}
      */
-    public function findNextScheduled(\DateTimeImmutable $dateTime = null, array $skippedExecutions = [])
+    public function findNextScheduled(?\DateTimeImmutable $dateTime = null, array $skippedExecutions = [])
     {
         $queryBuilder = $this->createQueryBuilder('e')
             ->innerJoin('e.task', 't')
diff --git a/src/EventListener/DoctrineTaskExecutionListener.php b/src/EventListener/DoctrineTaskExecutionListener.php
index 8979876..d1a0114 100644
--- a/src/EventListener/DoctrineTaskExecutionListener.php
+++ b/src/EventListener/DoctrineTaskExecutionListener.php
@@ -27,7 +27,7 @@ class DoctrineTaskExecutionListener
     /**
      * @param EntityManagerInterface $entityManager
      */
-    public function __construct(EntityManagerInterface $entityManager = null)
+    public function __construct(?EntityManagerInterface $entityManager = null)
     {
         $this->entityManager = $entityManager;
     }
diff --git a/tests/Functional/BaseCommandTestCase.php b/tests/Functional/BaseCommandTestCase.php
index cf40ee8..ffc29d7 100644
--- a/tests/Functional/BaseCommandTestCase.php
+++ b/tests/Functional/BaseCommandTestCase.php
@@ -98,7 +98,7 @@ protected function setUp(): void
      *
      * @return TaskInterface
      */
-    protected function createTask($workload, CronExpression $cronExpression = null, $handlerClass = TestHandler::class)
+    protected function createTask($workload, ?CronExpression $cronExpression = null, $handlerClass = TestHandler::class)
     {
         $task = $this->taskRepository->create($handlerClass, $workload);
         if ($cronExpression) {
diff --git a/tests/Functional/Entity/TaskExecutionRepositoryTest.php b/tests/Functional/Entity/TaskExecutionRepositoryTest.php
index b4012e8..32fccd4 100644
--- a/tests/Functional/Entity/TaskExecutionRepositoryTest.php
+++ b/tests/Functional/Entity/TaskExecutionRepositoryTest.php
@@ -187,7 +187,7 @@ public function testFindScheduledSkipped()
      *
      * @return TaskExecutionInterface
      */
-    private function save(TaskInterface $task = null, \DateTimeImmutable $scheduleTime = null, $status = TaskStatus::PLANNED)
+    private function save(?TaskInterface $task = null, ?\DateTimeImmutable $scheduleTime = null, $status = TaskStatus::PLANNED)
     {
         if (!$scheduleTime) {
             $scheduleTime = new \DateTimeImmutable();