diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 7f59b9a2..c92f166a 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        php: [8.2, 8.3]
+        php: [8.2, 8.3, 8.4]
         laravel: [11]
 
     steps:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 118e3b11..7ebc2cca 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file. This projec
 
 ## Unreleased
 
+### Changed
+
+- Removed PHP 8.4 deprecation notices.
+
 ## [7.0.0] - 2024-03-14
 
 ### Changed
diff --git a/composer.json b/composer.json
index 790fa7c4..26a21ce6 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,7 @@
     "require": {
         "php": "^8.2",
         "ext-json": "*",
-        "laravel-json-api/neomerx-json-api": "^5.0.2",
+        "laravel-json-api/neomerx-json-api": "^5.0.3",
         "laravel/framework": "^11.0",
         "nyholm/psr7": "^1.8",
         "ramsey/uuid": "^4.0",
diff --git a/src/Api/Repository.php b/src/Api/Repository.php
index 10d8cfdd..4d38efc4 100644
--- a/src/Api/Repository.php
+++ b/src/Api/Repository.php
@@ -72,7 +72,7 @@ public function exists($apiName)
      *      route parameters, if needed.
      * @return Api
      */
-    public function createApi(string $apiName, string $host = null, array $parameters = [])
+    public function createApi(string $apiName, ?string $host = null, array $parameters = [])
     {
         $config = $this->configFor($apiName);
         $config = $this->normalize($config, $host);
diff --git a/src/Broadcasting/BroadcastsData.php b/src/Broadcasting/BroadcastsData.php
index a2dfefbd..8ae523e1 100644
--- a/src/Broadcasting/BroadcastsData.php
+++ b/src/Broadcasting/BroadcastsData.php
@@ -51,7 +51,7 @@ protected function broadcastEncoder()
      * @param array|null $fieldsets
      * @return array
      */
-    protected function serializeData($data, $includePaths = null, array $fieldsets = null)
+    protected function serializeData($data, $includePaths = null, ?array $fieldsets = null)
     {
         $params = new QueryParameters($includePaths ? (array) $includePaths : null, $fieldsets);
 
diff --git a/src/Client/AbstractClient.php b/src/Client/AbstractClient.php
index b65db7ec..3a5c488e 100644
--- a/src/Client/AbstractClient.php
+++ b/src/Client/AbstractClient.php
@@ -72,7 +72,7 @@ abstract class AbstractClient implements ClientInterface
     abstract protected function request(
         $method,
         $uri,
-        array $payload = null,
+        ?array $payload = null,
         array $parameters = []
     );
 
diff --git a/src/Client/GuzzleClient.php b/src/Client/GuzzleClient.php
index d67dc6cc..2a75b629 100644
--- a/src/Client/GuzzleClient.php
+++ b/src/Client/GuzzleClient.php
@@ -60,7 +60,7 @@ public function __construct(
     protected function request(
         $method,
         $uri,
-        array $payload = null,
+        ?array $payload = null,
         array $parameters = []
     ) {
         $request = new Request($method, $uri);
diff --git a/src/Codec/Encoding.php b/src/Codec/Encoding.php
index 81353544..1801b164 100644
--- a/src/Codec/Encoding.php
+++ b/src/Codec/Encoding.php
@@ -54,7 +54,7 @@ class Encoding
     public static function create(
         $mediaType,
         int $options = 0,
-        string $urlPrefix = null,
+        ?string $urlPrefix = null,
         int $depth = 512
     ): self
     {
@@ -73,7 +73,7 @@ public static function create(
      * @param int $depth
      * @return Encoding
      */
-    public static function jsonApi(int $options = 0, string $urlPrefix = null, int $depth = 512): self
+    public static function jsonApi(int $options = 0, ?string $urlPrefix = null, int $depth = 512): self
     {
         return self::create(
             MediaTypeInterface::JSON_API_MEDIA_TYPE,
@@ -104,7 +104,7 @@ public static function custom($mediaType): self
      * @param string|null $urlPrefix
      * @return Encoding
      */
-    public static function fromArray($key, $value, string $urlPrefix = null): self
+    public static function fromArray($key, $value, ?string $urlPrefix = null): self
     {
         if (is_numeric($key)) {
             $key = $value;
diff --git a/src/Codec/EncodingList.php b/src/Codec/EncodingList.php
index 87eac050..caf408b1 100644
--- a/src/Codec/EncodingList.php
+++ b/src/Codec/EncodingList.php
@@ -47,7 +47,7 @@ class EncodingList implements IteratorAggregate, Countable
      * @param string|null $urlPrefix
      * @return EncodingList
      */
-    public static function fromArray(iterable $config, string $urlPrefix = null): self
+    public static function fromArray(iterable $config, ?string $urlPrefix = null): self
     {
         $values = Collection::make($config)
             ->map(fn($value, $key) => Encoding::fromArray($key, $value, $urlPrefix))
diff --git a/src/Container.php b/src/Container.php
index 903d7a82..4c1362fa 100644
--- a/src/Container.php
+++ b/src/Container.php
@@ -379,7 +379,7 @@ protected function getCreatedAdapter($resourceType)
      * @param ResourceAdapterInterface|null $adapter
      * @return void
      */
-    protected function setCreatedAdapter($resourceType, ResourceAdapterInterface $adapter = null)
+    protected function setCreatedAdapter($resourceType, ?ResourceAdapterInterface $adapter = null)
     {
         $this->createdAdapters[$resourceType] = $adapter;
     }
@@ -467,7 +467,7 @@ protected function getCreatedAuthorizer($resourceType)
      * @param AuthorizerInterface|null $authorizer
      * @return void
      */
-    protected function setCreatedAuthorizer($resourceType, AuthorizerInterface $authorizer = null)
+    protected function setCreatedAuthorizer($resourceType, ?AuthorizerInterface $authorizer = null)
     {
         $this->createdAuthorizers[$resourceType] = $authorizer;
     }
diff --git a/src/Contracts/Schema/SchemaProviderInterface.php b/src/Contracts/Schema/SchemaProviderInterface.php
index 910bc25c..3753a6a6 100644
--- a/src/Contracts/Schema/SchemaProviderInterface.php
+++ b/src/Contracts/Schema/SchemaProviderInterface.php
@@ -78,7 +78,7 @@ public function getRelationships(object $resource, bool $isPrimary, array $inclu
      * @param object|null $resource
      * @return string
      */
-    public function getSelfSubUrl(object $resource = null): string;
+    public function getSelfSubUrl(?object $resource = null): string;
 
     /**
      * Get the resource self sub link.
diff --git a/src/Document/Error/Error.php b/src/Document/Error/Error.php
index 6937a41c..f2f7a195 100644
--- a/src/Document/Error/Error.php
+++ b/src/Document/Error/Error.php
@@ -134,12 +134,12 @@ public static function fromArray(array $input): self
     public function __construct(
         $id = null,
         $status = null,
-        string $code = null,
-        string $title = null,
-        string $detail = null,
-        iterable $source = null,
-        iterable $links = null,
-        iterable $meta = null
+        ?string $code = null,
+        ?string $title = null,
+        ?string $detail = null,
+        ?iterable $source = null,
+        ?iterable $links = null,
+        ?iterable $meta = null
     )
     {
         $this->setId($id);
diff --git a/src/Document/Error/Translator.php b/src/Document/Error/Translator.php
index 5f5fd032..ca7b5963 100644
--- a/src/Document/Error/Translator.php
+++ b/src/Document/Error/Translator.php
@@ -17,6 +17,7 @@
 
 namespace CloudCreativity\LaravelJsonApi\Document\Error;
 
+use Closure;
 use CloudCreativity\LaravelJsonApi\Exceptions\ValidationException;
 use CloudCreativity\LaravelJsonApi\LaravelJsonApi;
 use CloudCreativity\LaravelJsonApi\Utils\Str;
@@ -402,7 +403,7 @@ public function resourceFieldExistsInAttributesAndRelationships(
      * @param string|null $detail
      * @return ErrorInterface
      */
-    public function resourceCannotBeDeleted(string $detail = null): ErrorInterface
+    public function resourceCannotBeDeleted(?string $detail = null): ErrorInterface
     {
         return new NeomerxError(
             null,
@@ -475,11 +476,11 @@ public function invalidQueryParameter(string $param, ?string $detail = null, arr
      * Create errors for a failed validator.
      *
      * @param ValidatorContract $validator
-     * @param \Closure|null $closure
+     * @param Closure|null $closure
      *      a closure that is bound to the translator.
      * @return ErrorCollection
      */
-    public function failedValidator(ValidatorContract $validator, \Closure $closure = null): ErrorCollection
+    public function failedValidator(ValidatorContract $validator, ?Closure $closure = null): ErrorCollection
     {
         $failed = $this->doesIncludeFailed() ? $validator->failed() : [];
         $errors = new ErrorCollection();
@@ -513,12 +514,12 @@ public function failedValidator(ValidatorContract $validator, \Closure $closure
      * Create a JSON API exception for a failed validator.
      *
      * @param ValidatorContract $validator
-     * @param \Closure|null $closure
+     * @param Closure|null $closure
      * @return JsonApiException
      */
     public function failedValidatorException(
         ValidatorContract $validator,
-        \Closure $closure = null
+        ?Closure $closure = null
     ): JsonApiException
     {
         return new ValidationException(
@@ -529,11 +530,11 @@ public function failedValidatorException(
     /**
      * Create an error by calling the closure with it bound to the error translator.
      *
-     * @param \Closure $closure
+     * @param Closure $closure
      * @param mixed ...$args
      * @return ErrorInterface
      */
-    public function call(\Closure $closure, ...$args): ErrorInterface
+    public function call(Closure $closure, ...$args): ErrorInterface
     {
         return $closure->call($this, ...$args);
     }
diff --git a/src/Eloquent/AbstractAdapter.php b/src/Eloquent/AbstractAdapter.php
index 02a4a64f..5129855d 100644
--- a/src/Eloquent/AbstractAdapter.php
+++ b/src/Eloquent/AbstractAdapter.php
@@ -17,6 +17,7 @@
 
 namespace CloudCreativity\LaravelJsonApi\Eloquent;
 
+use Closure;
 use CloudCreativity\LaravelJsonApi\Adapter\AbstractResourceAdapter;
 use CloudCreativity\LaravelJsonApi\Contracts\Adapter\HasManyAdapterInterface;
 use CloudCreativity\LaravelJsonApi\Contracts\Adapter\RelationshipAdapterInterface;
@@ -115,7 +116,7 @@ abstract protected function filter($query, Collection $filters);
      * @param Model $model
      * @param PagingStrategyInterface|null $paging
      */
-    public function __construct(Model $model, PagingStrategyInterface $paging = null)
+    public function __construct(Model $model, ?PagingStrategyInterface $paging = null)
     {
         $this->model = $model;
         $this->paging = $paging;
@@ -259,11 +260,11 @@ public function addScopes(Scope ...$scopes): self
     /**
      * Add a global scope using a closure.
      *
-     * @param \Closure $scope
+     * @param Closure $scope
      * @param string|null $identifier
      * @return $this
      */
-    public function addClosureScope(\Closure $scope, string $identifier = null): self
+    public function addClosureScope(Closure $scope, ?string $identifier = null): self
     {
         $identifier = $identifier ?: spl_object_hash($scope);
 
@@ -616,20 +617,20 @@ protected function morphMany(HasManyAdapterInterface ...$adapters)
     }
 
     /**
-     * @param \Closure $factory
+     * @param Closure $factory
      *      a factory that creates a new Eloquent query builder.
      * @return QueriesMany
      */
-    protected function queriesMany(\Closure $factory)
+    protected function queriesMany(Closure $factory)
     {
         return new QueriesMany($factory);
     }
 
     /**
-     * @param \Closure $factory
+     * @param Closure $factory
      * @return QueriesOne
      */
-    protected function queriesOne(\Closure $factory)
+    protected function queriesOne(Closure $factory)
     {
         return new QueriesOne($factory);
     }
diff --git a/src/Encoder/EncoderOptions.php b/src/Encoder/EncoderOptions.php
index 400e6e93..65b0b0ca 100644
--- a/src/Encoder/EncoderOptions.php
+++ b/src/Encoder/EncoderOptions.php
@@ -43,7 +43,7 @@ class EncoderOptions
      * @param string|null $urlPrefix
      * @param int $depth
      */
-    public function __construct(int $options = 0, string $urlPrefix = null, int $depth = 512)
+    public function __construct(int $options = 0, ?string $urlPrefix = null, int $depth = 512)
     {
         $this->options   = $options;
         $this->depth     = $depth;
diff --git a/src/Exceptions/ClientException.php b/src/Exceptions/ClientException.php
index 870d7486..df6fd921 100644
--- a/src/Exceptions/ClientException.php
+++ b/src/Exceptions/ClientException.php
@@ -17,6 +17,7 @@
 
 namespace CloudCreativity\LaravelJsonApi\Exceptions;
 
+use Exception;
 use Illuminate\Support\Collection;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
@@ -50,12 +51,12 @@ class ClientException extends \RuntimeException
      *
      * @param RequestInterface $request
      * @param ResponseInterface|null $response
-     * @param \Exception|null $previous
+     * @param Exception|null $previous
      */
     public function __construct(
         RequestInterface $request,
-        ResponseInterface $response = null,
-        \Exception $previous = null
+        ?ResponseInterface $response = null,
+        ?Exception $previous = null
     ) {
         parent::__construct(
             $previous ? $previous->getMessage() : 'Client encountered an error.',
@@ -104,7 +105,7 @@ public function getErrors()
 
         try {
             $this->errors = $this->parse();
-        } catch (\Exception $ex) {
+        } catch (Exception $ex) {
             $this->errors = [];
         }
 
diff --git a/src/Exceptions/DocumentRequiredException.php b/src/Exceptions/DocumentRequiredException.php
index 82c8b047..c5d15750 100644
--- a/src/Exceptions/DocumentRequiredException.php
+++ b/src/Exceptions/DocumentRequiredException.php
@@ -35,7 +35,7 @@ class DocumentRequiredException extends InvalidJsonException
      *
      * @param Exception|null $previous
      */
-    public function __construct(Exception $previous = null)
+    public function __construct(?Exception $previous = null)
     {
         parent::__construct(
             null,
diff --git a/src/Exceptions/InvalidJsonException.php b/src/Exceptions/InvalidJsonException.php
index 88ff9d05..dcc4586e 100644
--- a/src/Exceptions/InvalidJsonException.php
+++ b/src/Exceptions/InvalidJsonException.php
@@ -44,7 +44,7 @@ class InvalidJsonException extends JsonApiException
      * @param Exception|null $previous
      * @return InvalidJsonException
      */
-    public static function create($defaultHttpCode = self::HTTP_CODE_BAD_REQUEST, Exception $previous = null)
+    public static function create($defaultHttpCode = self::HTTP_CODE_BAD_REQUEST, ?Exception $previous = null)
     {
         return new self(json_last_error(), json_last_error_msg(), $defaultHttpCode, $previous);
     }
@@ -61,7 +61,7 @@ public function __construct(
         $jsonError = null,
         $jsonErrorMessage = null,
         $defaultHttpCode = self::HTTP_CODE_BAD_REQUEST,
-        Exception $previous = null
+        ?Exception $previous = null
     ) {
         parent::__construct([], $defaultHttpCode, $previous);
 
diff --git a/src/Exceptions/JsonApiException.php b/src/Exceptions/JsonApiException.php
index e76207e8..ee3fbafc 100644
--- a/src/Exceptions/JsonApiException.php
+++ b/src/Exceptions/JsonApiException.php
@@ -46,7 +46,7 @@ class JsonApiException extends Exception implements HttpExceptionInterface, Resp
      * @param Throwable|null $previous
      * @return static
      */
-    public static function make($errors, Throwable $previous = null): self
+    public static function make($errors, ?Throwable $previous = null): self
     {
         return new self($errors, $previous);
     }
@@ -58,7 +58,7 @@ public static function make($errors, Throwable $previous = null): self
      * @param Throwable|null $previous
      * @param array $headers
      */
-    public function __construct($errors, Throwable $previous = null, array $headers = [])
+    public function __construct($errors, ?Throwable $previous = null, array $headers = [])
     {
         parent::__construct('JSON API error', 0, $previous);
         $this->errors = Errors::cast($errors);
diff --git a/src/Exceptions/ResourceNotFoundException.php b/src/Exceptions/ResourceNotFoundException.php
index d39c1d62..63772d58 100644
--- a/src/Exceptions/ResourceNotFoundException.php
+++ b/src/Exceptions/ResourceNotFoundException.php
@@ -17,6 +17,7 @@
 
 namespace CloudCreativity\LaravelJsonApi\Exceptions;
 
+use Exception;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 
 class ResourceNotFoundException extends NotFoundHttpException
@@ -37,14 +38,14 @@ class ResourceNotFoundException extends NotFoundHttpException
      *
      * @param string $type
      * @param string $id
-     * @param \Exception|null $previous
+     * @param Exception|null $previous
      * @param int $code
      * @param array $headers
      */
     public function __construct(
         string $type,
         string $id,
-        \Exception $previous = null,
+        ?Exception $previous = null,
         int $code = 0,
         array $headers = []
     ) {
diff --git a/src/Exceptions/ValidationException.php b/src/Exceptions/ValidationException.php
index df909d16..076c95d4 100644
--- a/src/Exceptions/ValidationException.php
+++ b/src/Exceptions/ValidationException.php
@@ -59,7 +59,7 @@ public static function create(ValidatorInterface $validator): self
      * @param string|int|null $defaultHttpCode
      * @param Exception|null $previous
      */
-    public function __construct($errors, $defaultHttpCode = self::DEFAULT_HTTP_CODE, Exception $previous = null)
+    public function __construct($errors, $defaultHttpCode = self::DEFAULT_HTTP_CODE, ?Exception $previous = null)
     {
         parent::__construct(
             $errors,
diff --git a/src/Factories/Factory.php b/src/Factories/Factory.php
index 1f732964..4cbea344 100644
--- a/src/Factories/Factory.php
+++ b/src/Factories/Factory.php
@@ -19,6 +19,7 @@
 
 namespace CloudCreativity\LaravelJsonApi\Factories;
 
+use Closure;
 use CloudCreativity\LaravelJsonApi\Api\AbstractProvider;
 use CloudCreativity\LaravelJsonApi\Api\Api;
 use CloudCreativity\LaravelJsonApi\Api\LinkGenerator;
@@ -217,12 +218,12 @@ public function createStore(ContainerInterface $container): StoreInterface
      */
     public function createPage(
         $data,
-        LinkInterface $first = null,
-        LinkInterface $previous = null,
-        LinkInterface $next = null,
-        LinkInterface $last = null,
+        ?LinkInterface $first = null,
+        ?LinkInterface $previous = null,
+        ?LinkInterface $next = null,
+        ?LinkInterface $last = null,
         $meta = null,
-        string $metaKey = null
+        ?string $metaKey = null
     ): PageInterface
     {
         return new Page($data, $first, $previous, $next, $last, $meta, $metaKey);
@@ -285,12 +286,12 @@ public function createLinkGenerator(UrlGenerator $urls): LinkGenerator
      * @return QueryParameters
      */
     public function createQueryParameters(
-        array $includePaths = null,
-        array $fieldSets = null,
-        array $sortParameters = null,
-        array $pagingParameters = null,
-        array $filteringParameters = null,
-        array $unrecognizedParams = null
+        ?array $includePaths = null,
+        ?array $fieldSets = null,
+        ?array $sortParameters = null,
+        ?array $pagingParameters = null,
+        ?array $filteringParameters = null,
+        ?array $unrecognizedParams = null
     ) {
         return new QueryParameters(
             $includePaths,
@@ -420,7 +421,7 @@ public function createDocumentMapper(): Mapper
      * @param array $rules
      * @param array $messages
      * @param array $customAttributes
-     * @param \Closure|null $callback
+     * @param Closure|null $callback
      *       a closure for creating an error, that will be bound to the error translator.
      * @return ValidatorInterface
      */
@@ -429,7 +430,7 @@ public function createValidator(
         array $rules,
         array $messages = [],
         array $customAttributes = [],
-        \Closure $callback = null
+        ?Closure $callback = null
     ): ValidatorInterface
     {
         $translator = $this->createErrorTranslator();
diff --git a/src/Http/Headers/HeaderParameters.php b/src/Http/Headers/HeaderParameters.php
index f9c64a51..80f939d4 100644
--- a/src/Http/Headers/HeaderParameters.php
+++ b/src/Http/Headers/HeaderParameters.php
@@ -41,7 +41,7 @@ class HeaderParameters implements HeaderParametersInterface
      * @param AcceptHeaderInterface $accept
      * @param HeaderInterface|null $contentType
      */
-    public function __construct(AcceptHeaderInterface $accept, HeaderInterface $contentType = null)
+    public function __construct(AcceptHeaderInterface $accept, ?HeaderInterface $contentType = null)
     {
         $this->accept = $accept;
         $this->contentType = $contentType;
diff --git a/src/Http/Middleware/NegotiateContent.php b/src/Http/Middleware/NegotiateContent.php
index e15002fe..4145f5d5 100644
--- a/src/Http/Middleware/NegotiateContent.php
+++ b/src/Http/Middleware/NegotiateContent.php
@@ -80,7 +80,7 @@ public function __construct(Container $container, Factory $factory, Route $route
      * @return mixed
      * @throws HttpException
      */
-    public function handle($request, \Closure $next, string $default = null)
+    public function handle($request, \Closure $next, ?string $default = null)
     {
         $api = $this->container->make(Api::class);
         /** @var HeaderParametersInterface $headers */
diff --git a/src/Http/Query/QueryParameters.php b/src/Http/Query/QueryParameters.php
index 2b6d3da1..80afd8e5 100644
--- a/src/Http/Query/QueryParameters.php
+++ b/src/Http/Query/QueryParameters.php
@@ -93,12 +93,12 @@ public static function cast(QueryParametersInterface $parameters)
      * @param array|null $unrecognizedParams
      */
     public function __construct(
-        array $includePaths = null,
-        array $fieldSets = null,
-        array $sortParameters = null,
-        array $pagingParameters = null,
-        array $filteringParameters = null,
-        array $unrecognizedParams = null
+        ?array $includePaths = null,
+        ?array $fieldSets = null,
+        ?array $sortParameters = null,
+        ?array $pagingParameters = null,
+        ?array $filteringParameters = null,
+        ?array $unrecognizedParams = null
     ) {
         $this->fieldSets = $fieldSets;
         $this->includePaths = $includePaths;
diff --git a/src/Http/Responses/Responses.php b/src/Http/Responses/Responses.php
index 6cdde794..d571afda 100644
--- a/src/Http/Responses/Responses.php
+++ b/src/Http/Responses/Responses.php
@@ -262,7 +262,7 @@ public function content(
     public function getContentResponseBackwardsCompat(
         $data,
         int $statusCode = self::HTTP_OK,
-        array $links = null,
+        ?array $links = null,
         $meta = null,
         array $headers = []
     ): Response
@@ -423,7 +423,7 @@ public function relationship(
     public function getIdentifiersResponseBackwardsCompat(
         $data,
         int $statusCode = self::HTTP_OK,
-        array $links = null,
+        ?array $links = null,
         $meta = null,
         array $headers = []
     ): Response {
@@ -444,7 +444,7 @@ public function getIdentifiersResponseBackwardsCompat(
      * @param array $headers
      * @return Response
      */
-    public function error($error, int $defaultStatusCode = null, array $headers = []): Response
+    public function error($error, ?int $defaultStatusCode = null, array $headers = []): Response
     {
         if (!$error instanceof ErrorInterface) {
             $error = $this->factory->createDocumentMapper()->createError(
@@ -468,7 +468,7 @@ public function error($error, int $defaultStatusCode = null, array $headers = []
      *
      * @return Response
      */
-    public function errors(iterable $errors, int $defaultStatusCode = null, array $headers = []): Response
+    public function errors(iterable $errors, ?int $defaultStatusCode = null, array $headers = []): Response
     {
         $errors = $this->factory->createDocumentMapper()->createErrors($errors);
         $statusCode = Helpers::httpErrorStatus($errors, $defaultStatusCode);
diff --git a/src/Pagination/Page.php b/src/Pagination/Page.php
index 37d3bf70..f04f31be 100644
--- a/src/Pagination/Page.php
+++ b/src/Pagination/Page.php
@@ -76,12 +76,12 @@ class Page implements PageInterface
      */
     public function __construct(
         $data,
-        LinkInterface $first = null,
-        LinkInterface $previous = null,
-        LinkInterface $next = null,
-        LinkInterface $last = null,
+        ?LinkInterface $first = null,
+        ?LinkInterface $previous = null,
+        ?LinkInterface $next = null,
+        ?LinkInterface $last = null,
         $meta = null,
-        string $metaKey = null
+        ?string $metaKey = null
     ) {
         $this->data = $data;
         $this->first = $first;
diff --git a/src/Queue/AsyncSchema.php b/src/Queue/AsyncSchema.php
index 285b1cbf..f667a340 100644
--- a/src/Queue/AsyncSchema.php
+++ b/src/Queue/AsyncSchema.php
@@ -38,7 +38,7 @@ public function getResourceType(): string
      * @param AsynchronousProcess|object|null $resource
      * @return string
      */
-    public function getSelfSubUrl(object $resource = null): string
+    public function getSelfSubUrl(?object $resource = null): string
     {
         if (!$resource) {
             return '/' . $this->getResourceType();
diff --git a/src/Queue/ClientDispatch.php b/src/Queue/ClientDispatch.php
index a538a22a..a30b1c34 100644
--- a/src/Queue/ClientDispatch.php
+++ b/src/Queue/ClientDispatch.php
@@ -83,7 +83,7 @@ public function setApi(string $api): ClientDispatch
      * @param string|null $id
      * @return ClientDispatch
      */
-    public function setResource(string $type, string $id = null): ClientDispatch
+    public function setResource(string $type, ?string $id = null): ClientDispatch
     {
         $this->resourceType = $type;
         $this->resourceId = $id;
diff --git a/src/Routing/JsonApiRegistrar.php b/src/Routing/JsonApiRegistrar.php
index 7cb0ff36..1edad1f7 100644
--- a/src/Routing/JsonApiRegistrar.php
+++ b/src/Routing/JsonApiRegistrar.php
@@ -73,7 +73,7 @@ public function register(string $api): ApiRegistration
      * @param Closure|null $routes
      * @return ApiRegistration
      */
-    public function api(string $apiName, $options = [], Closure $routes = null): ApiRegistration
+    public function api(string $apiName, $options = [], ?Closure $routes = null): ApiRegistration
     {
         if ($options instanceof Closure) {
             $routes = $options;
diff --git a/src/Routing/RelationshipsRegistration.php b/src/Routing/RelationshipsRegistration.php
index 8312856d..66cddb0a 100644
--- a/src/Routing/RelationshipsRegistration.php
+++ b/src/Routing/RelationshipsRegistration.php
@@ -55,7 +55,7 @@ public function __construct($hasOne = [], $hasMany = [])
      * @param string|null $inverse
      * @return RelationshipRegistration
      */
-    public function hasOne(string $field, string $inverse = null): RelationshipRegistration
+    public function hasOne(string $field, ?string $inverse = null): RelationshipRegistration
     {
         $rel = $this->hasOne[$field] ?? new RelationshipRegistration();
 
@@ -71,7 +71,7 @@ public function hasOne(string $field, string $inverse = null): RelationshipRegis
      * @param string|null $inverse
      * @return RelationshipRegistration
      */
-    public function hasMany(string $field, string $inverse = null): RelationshipRegistration
+    public function hasMany(string $field, ?string $inverse = null): RelationshipRegistration
     {
         $rel = $this->hasMany[$field] ?? new RelationshipRegistration();
 
diff --git a/src/Routing/ResourceRegistrar.php b/src/Routing/ResourceRegistrar.php
index 5570bd46..6d511678 100644
--- a/src/Routing/ResourceRegistrar.php
+++ b/src/Routing/ResourceRegistrar.php
@@ -17,6 +17,7 @@
 
 namespace CloudCreativity\LaravelJsonApi\Routing;
 
+use Closure;
 use Illuminate\Contracts\Routing\Registrar;
 use Illuminate\Routing\Route;
 use Illuminate\Support\Str;
@@ -50,7 +51,7 @@ final class ResourceRegistrar
     use RegistersResources;
 
     /**
-     * @var \Closure|null
+     * @var Closure|null
      */
     private $group;
 
@@ -60,9 +61,9 @@ final class ResourceRegistrar
      * @param Registrar $router
      * @param string $resourceType
      * @param array $options
-     * @param \Closure|null $group
+     * @param Closure|null $group
      */
-    public function __construct(Registrar $router, string $resourceType, array $options = [], \Closure $group = null)
+    public function __construct(Registrar $router, string $resourceType, array $options = [], ?Closure $group = null)
     {
         $this->router = $router;
         $this->resourceType = $resourceType;
diff --git a/src/Routing/RouteRegistration.php b/src/Routing/RouteRegistration.php
index 4c61555a..98dfc5d7 100644
--- a/src/Routing/RouteRegistration.php
+++ b/src/Routing/RouteRegistration.php
@@ -79,7 +79,7 @@ public function controller(string $controller): self
      * @param string|null $inverse
      * @return $this
      */
-    public function field(string $field, string $inverse = null): self
+    public function field(string $field, ?string $inverse = null): self
     {
         $this->defaults = array_merge($this->defaults, [
             ResourceRegistrar::PARAM_RELATIONSHIP_NAME => $field,
diff --git a/src/Rules/AbstractAllowedRule.php b/src/Rules/AbstractAllowedRule.php
index 29d30556..59c8edd6 100644
--- a/src/Rules/AbstractAllowedRule.php
+++ b/src/Rules/AbstractAllowedRule.php
@@ -54,7 +54,7 @@ abstract protected function extract($value): Collection;
      *
      * @param array|null $allowed
      */
-    public function __construct(array $allowed = null)
+    public function __construct(?array $allowed = null)
     {
         $this->all = is_null($allowed);
         $this->allowed = collect($allowed)->combine($allowed);
diff --git a/src/Rules/AllowedFieldSets.php b/src/Rules/AllowedFieldSets.php
index becc63f7..c975dca4 100644
--- a/src/Rules/AllowedFieldSets.php
+++ b/src/Rules/AllowedFieldSets.php
@@ -50,7 +50,7 @@ class AllowedFieldSets implements Rule
      *
      * @param array|null $allowed
      */
-    public function __construct(array $allowed = null)
+    public function __construct(?array $allowed = null)
     {
         $this->all = is_null($allowed);
         $this->allowed = collect($allowed);
@@ -64,7 +64,7 @@ public function __construct(array $allowed = null)
      *      the allowed fields, empty array for none allowed, or null for all allowed.
      * @return $this
      */
-    public function allow(string $resourceType, array $fields = null): self
+    public function allow(string $resourceType, ?array $fields = null): self
     {
         $this->all = false;
         $this->allowed[$resourceType] = $fields;
diff --git a/src/Schema/Schema.php b/src/Schema/Schema.php
index 08906daf..babee392 100644
--- a/src/Schema/Schema.php
+++ b/src/Schema/Schema.php
@@ -47,7 +47,7 @@ class Schema extends BaseSchema
     public function __construct(
         FactoryInterface $factory,
         SchemaProviderInterface $provider,
-        SchemaFields $fields = null
+        ?SchemaFields $fields = null,
     ) {
         parent::__construct($factory);
         $this->provider = $provider;
diff --git a/src/Schema/SchemaContainer.php b/src/Schema/SchemaContainer.php
index 1738ce1f..abafdfd5 100644
--- a/src/Schema/SchemaContainer.php
+++ b/src/Schema/SchemaContainer.php
@@ -48,7 +48,7 @@ class SchemaContainer implements SchemaContainerInterface
      * @param FactoryInterface $factory
      * @param SchemaFields|null $fields
      */
-    public function __construct(ContainerInterface $container, FactoryInterface $factory, SchemaFields $fields = null)
+    public function __construct(ContainerInterface $container, FactoryInterface $factory, ?SchemaFields $fields = null)
     {
         $this->container = $container;
         $this->factory = $factory;
diff --git a/src/Schema/SchemaFields.php b/src/Schema/SchemaFields.php
index 3a70c579..47a20b3b 100644
--- a/src/Schema/SchemaFields.php
+++ b/src/Schema/SchemaFields.php
@@ -83,7 +83,7 @@ public static function make(?QueryParametersInterface $parameters): self
      * @param iterable|null $paths
      * @param iterable|null $fieldSets
      */
-    public function __construct(iterable $paths = null, iterable $fieldSets = null)
+    public function __construct(?iterable $paths = null, ?iterable $fieldSets = null)
     {
         if (null !== $paths) {
             foreach ($paths as $path) {
diff --git a/src/Schema/SchemaProvider.php b/src/Schema/SchemaProvider.php
index 91152d6b..698529f5 100644
--- a/src/Schema/SchemaProvider.php
+++ b/src/Schema/SchemaProvider.php
@@ -116,7 +116,7 @@ public function getRelationships(object $resource, bool $isPrimary, array $inclu
     /**
      * @inheritDoc
      */
-    public function getSelfSubUrl(object $resource = null): string
+    public function getSelfSubUrl(?object $resource = null): string
     {
         if (empty($this->selfSubUrl)) {
             $this->selfSubUrl = '/' . $this->getResourceType();
@@ -213,7 +213,7 @@ protected function getContext(): ContextInterface
      * @param bool $treatAsHref
      * @return LinkInterface
      */
-    protected function createLink(string $subHref, array $meta = null, bool $treatAsHref = false): LinkInterface
+    protected function createLink(string $subHref, ?array $meta = null, bool $treatAsHref = false): LinkInterface
     {
         return $this->factory->createLink(!$treatAsHref, $subHref, !empty($meta), $meta);
     }
diff --git a/src/Services/JsonApiService.php b/src/Services/JsonApiService.php
index e5897975..bc323df8 100644
--- a/src/Services/JsonApiService.php
+++ b/src/Services/JsonApiService.php
@@ -115,7 +115,7 @@ public function requestApiOrFail()
      * @param Closure|null $routes
      * @return ApiRegistration
      */
-    public function register($apiName, $options = [], Closure $routes = null): ApiRegistration
+    public function register($apiName, $options = [], ?Closure $routes = null): ApiRegistration
     {
         /** @var JsonApiRegistrar $registrar */
         $registrar = app('json-api.registrar');
diff --git a/src/Utils/Helpers.php b/src/Utils/Helpers.php
index 01aaf6bb..e22f1706 100644
--- a/src/Utils/Helpers.php
+++ b/src/Utils/Helpers.php
@@ -162,7 +162,7 @@ public static function isJsonApi($request)
      * @see https://jsonapi.org/format/#errors
      * @deprecated 3.0.0 use `Document\Error\Errors::getStatus()`
      */
-    public static function httpErrorStatus($errors, int $default = null): int
+    public static function httpErrorStatus($errors, ?int $default = null): int
     {
         if (\is_null($default)) {
             $default = SymfonyResponse::HTTP_BAD_REQUEST;
diff --git a/src/Validation/Validator.php b/src/Validation/Validator.php
index 256b46aa..fa44d8d8 100644
--- a/src/Validation/Validator.php
+++ b/src/Validation/Validator.php
@@ -17,6 +17,7 @@
 
 namespace CloudCreativity\LaravelJsonApi\Validation;
 
+use Closure;
 use CloudCreativity\LaravelJsonApi\Contracts\Validation\ValidatorInterface;
 use CloudCreativity\LaravelJsonApi\Document\Error\Translator as ErrorTranslator;
 use Illuminate\Contracts\Validation\Validator as ValidatorContract;
@@ -41,7 +42,7 @@ class Validator implements ValidatorInterface
     protected $translator;
 
     /**
-     * @var \Closure|null
+     * @var Closure|null
      */
     protected $callback;
 
@@ -50,12 +51,12 @@ class Validator implements ValidatorInterface
      *
      * @param ValidatorContract $validator
      * @param ErrorTranslator $translator
-     * @param \Closure|null $callback
+     * @param Closure|null $callback
      */
     public function __construct(
         ValidatorContract $validator,
         ErrorTranslator $translator,
-        \Closure $callback = null
+        ?Closure $callback = null
     ) {
         $this->validator = $validator;
         $this->translator = $translator;
diff --git a/tests/lib/Integration/Client/TestCase.php b/tests/lib/Integration/Client/TestCase.php
index b47c2331..aea3689d 100644
--- a/tests/lib/Integration/Client/TestCase.php
+++ b/tests/lib/Integration/Client/TestCase.php
@@ -83,7 +83,7 @@ protected function willSeeIdentifiers($data, $status = 200, array $headers = [])
      * @param array $headers
      * @return Response
      */
-    protected function willSeeResponse(array $json = null, $status = 200, array $headers = [])
+    protected function willSeeResponse(?array $json = null, $status = 200, array $headers = [])
     {
         if ($json) {
             $body = json_encode($json);
diff --git a/tests/lib/Integration/Http/Controllers/TestEvent.php b/tests/lib/Integration/Http/Controllers/TestEvent.php
index a7a7a7aa..da25c2c1 100644
--- a/tests/lib/Integration/Http/Controllers/TestEvent.php
+++ b/tests/lib/Integration/Http/Controllers/TestEvent.php
@@ -58,7 +58,7 @@ class TestEvent
     public function __construct(
         $hook,
         $record,
-        ValidatedRequest $request = null,
+        ?ValidatedRequest $request = null,
         $related = null
     ) {
         $this->hook = $hook;
diff --git a/tests/lib/Unit/View/RendererTest.php b/tests/lib/Unit/View/RendererTest.php
index 5dea7b12..8f81fb08 100644
--- a/tests/lib/Unit/View/RendererTest.php
+++ b/tests/lib/Unit/View/RendererTest.php
@@ -122,7 +122,7 @@ public function testEncodeWithParameters()
      * @param QueryParameters|null $parameters
      * @return object
      */
-    private function withEncoder($name = null, $options = 0, $depth = 512, QueryParameters $parameters = null)
+    private function withEncoder($name = null, $options = 0, $depth = 512, ?QueryParameters $parameters = null)
     {
         $post = (object) ['type' => 'posts', 'id' => '1'];