diff --git a/src/Authenticator.php b/src/Authenticator.php
index 33881b5..2df7e72 100644
--- a/src/Authenticator.php
+++ b/src/Authenticator.php
@@ -155,7 +155,7 @@ public function getLostPasswordHandler($link)
      * @param ValidationResult $result A validationresult which is either valid or contains the error message(s)
      * @return Member The matched member, or null if the authentication fails
      */
-    public function authenticate(array $data, HTTPRequest $request, ValidationResult &$result = null)
+    public function authenticate(array $data, HTTPRequest $request, ?ValidationResult &$result = null)
     {
         try {
             $this->service->enforceLogin($request);
@@ -189,7 +189,7 @@ public function authenticate(array $data, HTTPRequest $request, ValidationResult
      * @param ValidationResult $result
      * @return ValidationResult
      */
-    public function checkPassword(Member $member, $password, ValidationResult &$result = null)
+    public function checkPassword(Member $member, $password, ?ValidationResult &$result = null)
     {
         // No-op
     }
diff --git a/src/RealMeService.php b/src/RealMeService.php
index c874625..347edca 100644
--- a/src/RealMeService.php
+++ b/src/RealMeService.php
@@ -907,7 +907,7 @@ private function getRequestedAuthnContext()
      *
      * @return Auth
      */
-    public function getAuth(HTTPRequest $request = null)
+    public function getAuth(?HTTPRequest $request = null)
     {
         if (isset($this->auth)) {
             return $this->auth;