diff --git a/src/Entity/BlockedEmailAddressHash.php b/src/Entity/BlockedEmailAddressHash.php
index dda4274..5847f24 100644
--- a/src/Entity/BlockedEmailAddressHash.php
+++ b/src/Entity/BlockedEmailAddressHash.php
@@ -18,12 +18,12 @@ class BlockedEmailAddressHash implements BlockedEmailAddressHashInterface
 
     public static function fromEmailAddress(
         EmailAddress $emailAddress,
-        DateTimeImmutable $blockDate = null
+        ?DateTimeImmutable $blockDate = null
     ): BlockedEmailAddressHashInterface {
         return new self($emailAddress->getHash(), $blockDate);
     }
 
-    public function __construct(string $hash, DateTimeImmutable $blockDate = null)
+    public function __construct(string $hash, ?DateTimeImmutable $blockDate = null)
     {
         $this->hash = $hash;
         $this->blockDate = $blockDate ?? new DateTimeImmutable();
diff --git a/src/Entity/BlockedEmailAddressHashInterface.php b/src/Entity/BlockedEmailAddressHashInterface.php
index b62ba20..4e06a5b 100644
--- a/src/Entity/BlockedEmailAddressHashInterface.php
+++ b/src/Entity/BlockedEmailAddressHashInterface.php
@@ -7,7 +7,7 @@
 
 interface BlockedEmailAddressHashInterface
 {
-    public static function fromEmailAddress(EmailAddress $emailAddress, DateTimeImmutable $blockDate = null): self;
+    public static function fromEmailAddress(EmailAddress $emailAddress, ?DateTimeImmutable $blockDate = null): self;
 
     public function getBlockedUntilDate(DateInterval $blockDuration): DateTimeImmutable;
 }
diff --git a/src/Exception/EmailAddressCanNotBeHashedWithoutSecretException.php b/src/Exception/EmailAddressCanNotBeHashedWithoutSecretException.php
index 85b8ec6..6be8ac8 100644
--- a/src/Exception/EmailAddressCanNotBeHashedWithoutSecretException.php
+++ b/src/Exception/EmailAddressCanNotBeHashedWithoutSecretException.php
@@ -7,7 +7,7 @@
 
 class EmailAddressCanNotBeHashedWithoutSecretException extends WebfactoryNewsletterRegistrationException
 {
-    public function __construct(EmailAddress $emailAddress, $code = 0, Throwable $previous = null)
+    public function __construct(EmailAddress $emailAddress, $code = 0, ?Throwable $previous = null)
     {
         parent::__construct(
             'The email address "'.$emailAddress->getEmailAddress().'" could not be hashed as this email '
diff --git a/src/Exception/EmailAddressDoesNotMatchHashOfPendingOptInException.php b/src/Exception/EmailAddressDoesNotMatchHashOfPendingOptInException.php
index b381261..5b285a7 100644
--- a/src/Exception/EmailAddressDoesNotMatchHashOfPendingOptInException.php
+++ b/src/Exception/EmailAddressDoesNotMatchHashOfPendingOptInException.php
@@ -12,7 +12,7 @@ public function __construct(
         EmailAddress $emailAddress,
         PendingOptInInterface $pendingOptIn,
         $code = 0,
-        Throwable $previous = null
+        ?Throwable $previous = null
     ) {
         parent::__construct(
             'The email address "'.$emailAddress->getEmailAddress().'" does not correspond to the hash of the '
diff --git a/src/Exception/PendingOptInClassCouldNotBeDeterminedException.php b/src/Exception/PendingOptInClassCouldNotBeDeterminedException.php
index 509dd0c..1007aba 100644
--- a/src/Exception/PendingOptInClassCouldNotBeDeterminedException.php
+++ b/src/Exception/PendingOptInClassCouldNotBeDeterminedException.php
@@ -8,7 +8,7 @@
 
 class PendingOptInClassCouldNotBeDeterminedException extends WebfactoryNewsletterRegistrationException
 {
-    public function __construct($code = 0, Throwable $previous = null)
+    public function __construct($code = 0, ?Throwable $previous = null)
     {
         parent::__construct(
             'We were unable to determine your '.RecipientInterface::class.' implementation. Consider replacing'
diff --git a/src/Exception/PendingOptInIsOutdatedException.php b/src/Exception/PendingOptInIsOutdatedException.php
index 843baa2..96fa1ee 100644
--- a/src/Exception/PendingOptInIsOutdatedException.php
+++ b/src/Exception/PendingOptInIsOutdatedException.php
@@ -7,7 +7,7 @@
 
 class PendingOptInIsOutdatedException extends WebfactoryNewsletterRegistrationException
 {
-    public function __construct(PendingOptInInterface $pendingOptIn, $code = 0, Throwable $previous = null)
+    public function __construct(PendingOptInInterface $pendingOptIn, $code = 0, ?Throwable $previous = null)
     {
         parent::__construct(
             'The PendingOptIn with uuid '.$pendingOptIn->getUuid().' is outdated and can no longer be '
diff --git a/src/Exception/RecipientClassCouldNotBeDeterminedException.php b/src/Exception/RecipientClassCouldNotBeDeterminedException.php
index b48318d..39d4f13 100644
--- a/src/Exception/RecipientClassCouldNotBeDeterminedException.php
+++ b/src/Exception/RecipientClassCouldNotBeDeterminedException.php
@@ -8,7 +8,7 @@
 
 class RecipientClassCouldNotBeDeterminedException extends WebfactoryNewsletterRegistrationException
 {
-    public function __construct($code = 0, Throwable $previous = null)
+    public function __construct($code = 0, ?Throwable $previous = null)
     {
         parent::__construct(
             'We were unable to determine your '.RecipientInterface::class.' implementation. Consider replacing'
diff --git a/src/StartRegistration/HoneypotType.php b/src/StartRegistration/HoneypotType.php
index 77a67ba..f31565e 100644
--- a/src/StartRegistration/HoneypotType.php
+++ b/src/StartRegistration/HoneypotType.php
@@ -26,7 +26,7 @@ class HoneypotType extends AbstractType
     protected TranslatorInterface $translator;
     protected LoggerInterface $logger;
 
-    public function __construct(TranslatorInterface $translator, LoggerInterface $logger = null)
+    public function __construct(TranslatorInterface $translator, ?LoggerInterface $logger = null)
     {
         $this->translator = $translator;
         $this->logger = $logger ?: new NullLogger();