diff --git a/Auth/Base.php b/Auth/Base.php
index c8be304..d1daa2e 100644
--- a/Auth/Base.php
+++ b/Auth/Base.php
@@ -98,7 +98,7 @@ abstract class Base implements Auth
      */
     protected $logger;
 
-    public function __construct(LoggerInterface $logger = null)
+    public function __construct(?LoggerInterface $logger = null)
     {
         $this->logger = $logger ?: StaticContainer::get(LoggerInterface::class);
     }
@@ -290,7 +290,7 @@ protected function getUserForLogin()
         return $this->userForLogin;
     }
 
-    protected function tryFallbackAuth($onlySuperUsers = true, Auth $auth = null)
+    protected function tryFallbackAuth($onlySuperUsers = true, ?Auth $auth = null)
     {
         if (empty($auth)) {
             $auth = new \Piwik\Plugins\Login\Auth();
diff --git a/LdapInterop/UserAccessAttributeParser.php b/LdapInterop/UserAccessAttributeParser.php
index bd86487..f0133e7 100644
--- a/LdapInterop/UserAccessAttributeParser.php
+++ b/LdapInterop/UserAccessAttributeParser.php
@@ -110,7 +110,7 @@ class UserAccessAttributeParser
      */
     private $logger;
 
-    public function __construct(LoggerInterface $logger = null)
+    public function __construct(?LoggerInterface $logger = null)
     {
         $this->logger = $logger ?: StaticContainer::get(LoggerInterface::class);
     }
diff --git a/LdapInterop/UserAccessMapper.php b/LdapInterop/UserAccessMapper.php
index 4ff2285..8d18bb4 100644
--- a/LdapInterop/UserAccessMapper.php
+++ b/LdapInterop/UserAccessMapper.php
@@ -85,7 +85,7 @@ class UserAccessMapper
     /**
      * Constructor.
      */
-    public function __construct(LoggerInterface $logger = null)
+    public function __construct(?LoggerInterface $logger = null)
     {
         $this->logger = $logger ?: StaticContainer::get(LoggerInterface::class);
     }
diff --git a/LdapInterop/UserMapper.php b/LdapInterop/UserMapper.php
index 748eba8..6a2b87b 100644
--- a/LdapInterop/UserMapper.php
+++ b/LdapInterop/UserMapper.php
@@ -76,7 +76,7 @@ class UserMapper
     /**
      * Constructor.
      */
-    public function __construct(LoggerInterface $logger = null)
+    public function __construct(?LoggerInterface $logger = null)
     {
         $this->logger = $logger ?: StaticContainer::get(LoggerInterface::class);
     }
diff --git a/LdapInterop/UserSynchronizer.php b/LdapInterop/UserSynchronizer.php
index 758f45a..0b60fcf 100644
--- a/LdapInterop/UserSynchronizer.php
+++ b/LdapInterop/UserSynchronizer.php
@@ -108,7 +108,7 @@ class UserSynchronizer
      */
     public static $skipPasswordConfirmation = false;
 
-    public function __construct(LoggerInterface $logger = null)
+    public function __construct(?LoggerInterface $logger = null)
     {
         $this->logger = $logger ?: StaticContainer::get(LoggerInterface::class);
     }
diff --git a/Model/LdapUsers.php b/Model/LdapUsers.php
index 1627b9d..4eb26d2 100644
--- a/Model/LdapUsers.php
+++ b/Model/LdapUsers.php
@@ -119,7 +119,7 @@ class LdapUsers
     /**
      * Constructor.
      */
-    public function __construct(LoggerInterface $logger = null)
+    public function __construct(?LoggerInterface $logger = null)
     {
         $this->logger = $logger ?: StaticContainer::get(LoggerInterface::class);
     }