diff --git a/README.md b/README.md
index 4af1d7c..5381ef4 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ It’s powered by Phil Sturgeon’s excellent [Fractal](http://fractal.thephplea
 
 ## Requirements
 
-This plugin requires Craft CMS 4.0 or later.
+This plugin requires Craft CMS 4.0.0+ or 5.0.0+.
 
 ## Installation
 
diff --git a/composer.json b/composer.json
index dce219c..5b240b6 100644
--- a/composer.json
+++ b/composer.json
@@ -26,7 +26,7 @@
   "minimum-stability": "dev",
   "prefer-stable": true,
   "require": {
-    "craftcms/cms": "^4.0.0-RC3",
+    "craftcms/cms": "^4.0.0-RC3|^5.0.0-beta.1",
     "league/fractal": "^0.20.1"
   },
   "require-dev": {
diff --git a/composer.lock b/composer.lock
index d208f5b..5eab996 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "393695a3b1d1e9e19ee64298aa11306f",
+    "content-hash": "ae356faea7dac544d8d151d9ce97044b",
     "packages": [
         {
             "name": "cebe/markdown",
diff --git a/src/JsonFeedV1Serializer.php b/src/JsonFeedV1Serializer.php
index f48072e..e18b27e 100644
--- a/src/JsonFeedV1Serializer.php
+++ b/src/JsonFeedV1Serializer.php
@@ -40,8 +40,8 @@ public function meta(array $meta): array
      */
     public function paginator(PaginatorInterface $paginator): array
     {
-        $currentPage = (int)$paginator->getCurrentPage();
-        $lastPage = (int)$paginator->getLastPage();
+        $currentPage = $paginator->getCurrentPage();
+        $lastPage = $paginator->getLastPage();
 
         if ($currentPage < $lastPage) {
             return [
diff --git a/src/PaginatorAdapter.php b/src/PaginatorAdapter.php
index 236a7b4..22bc2ff 100644
--- a/src/PaginatorAdapter.php
+++ b/src/PaginatorAdapter.php
@@ -17,32 +17,32 @@ class PaginatorAdapter implements PaginatorInterface
     /**
      * @var int
      */
-    protected $elementsPerPage;
+    protected int $elementsPerPage;
 
     /**
      * @var int
      */
-    protected $totalElements;
+    protected int $totalElements;
 
     /**
      * @var string
      */
-    protected $pageParam;
+    protected string $pageParam;
 
     /**
      * @var int
      */
-    protected $totalPages;
+    protected int $totalPages;
 
     /**
      * @var int
      */
-    protected $currentPage;
+    protected int $currentPage;
 
     /**
      * @var int
      */
-    protected $count;
+    protected int $count;
 
     /**
      * Constructor
@@ -51,7 +51,7 @@ class PaginatorAdapter implements PaginatorInterface
      * @param integer $totalElements
      * @param string $pageParam
      */
-    public function __construct($elementsPerPage, $totalElements, $pageParam)
+    public function __construct(int $elementsPerPage, int $totalElements, string $pageParam)
     {
         $this->elementsPerPage = $elementsPerPage;
         $this->totalElements = $totalElements;
@@ -105,7 +105,7 @@ public function getCount(): int
      *
      * @param int $count
      */
-    public function setCount($count)
+    public function setCount(int $count): void
     {
         $this->count = $count;
     }
@@ -126,7 +126,7 @@ public function getPerPage(): int
      * @param int $page
      * @return string
      */
-    public function getUrl($page): string
+    public function getUrl(int $page): string
     {
         $request = Craft::$app->getRequest();
 
diff --git a/src/Plugin.php b/src/Plugin.php
index 4badd50..306afc1 100644
--- a/src/Plugin.php
+++ b/src/Plugin.php
@@ -26,12 +26,12 @@ class Plugin extends \craft\base\Plugin
      * @var array The default Fractal resource adapter configuration
      * @see getDefaultResourceAdapterConfig()
      */
-    private $_defaultResourceAdapterConfig;
+    private ?array $_defaultResourceAdapterConfig = null;
 
     /**
      * @inheritdoc
      */
-    public function init()
+    public function init(): void
     {
         parent::init();
 
@@ -59,7 +59,7 @@ function(RegisterCacheOptionsEvent $event) {
      * @param string $pattern
      * @return callable|array|ResourceAdapterInterface|null
      */
-    public function getEndpoint($pattern)
+    public function getEndpoint(string $pattern)
     {
         return $this->getSettings()->endpoints[$pattern] ?? null;
     }
@@ -83,7 +83,7 @@ public function getDefaultResourceAdapterConfig(): array
      *
      * @param RegisterUrlRulesEvent $event
      */
-    public function registerUrlRules(RegisterUrlRulesEvent $event)
+    public function registerUrlRules(RegisterUrlRulesEvent $event): void
     {
         foreach ($this->getSettings()->endpoints as $pattern => $config) {
             $event->rules[$pattern] = [
diff --git a/src/Settings.php b/src/Settings.php
index 743ca37..c4fdef3 100644
--- a/src/Settings.php
+++ b/src/Settings.php
@@ -20,7 +20,7 @@ class Settings extends Model
     /**
      * @var array The endpoint configurations.
      */
-    public $endpoints = [];
+    public array $endpoints = [];
 
     /**
      * Returns the default endpoint configuration.
@@ -28,7 +28,7 @@ class Settings extends Model
      * @return array The default endpoint configuration.
      * @since 2.6.0
      */
-    public function getDefaults()
+    public function getDefaults(): array
     {
         return is_callable($this->defaults) ? call_user_func($this->defaults) : $this->defaults;
     }
diff --git a/src/resources/ElementResource.php b/src/resources/ElementResource.php
index f4877a5..a549135 100644
--- a/src/resources/ElementResource.php
+++ b/src/resources/ElementResource.php
@@ -30,12 +30,12 @@ class ElementResource extends BaseObject implements ResourceAdapterInterface
     /**
      * @var string The element type class name
      */
-    public $elementType;
+    public string $elementType;
 
     /**
      * @var array The element criteria params that should be used to filter the matching elements
      */
-    public $criteria = [];
+    public array $criteria = [];
 
     /**
      * @var callable|string|array|TransformerAbstract The transformer config, or an actual transformer object
@@ -45,34 +45,34 @@ class ElementResource extends BaseObject implements ResourceAdapterInterface
     /**
      * @var bool Whether to only return one result
      */
-    public $one = false;
+    public bool $one = false;
 
     /**
      * @var bool Whether to paginate the results
      */
-    public $paginate = true;
+    public bool $paginate = true;
 
     /**
      * @var int The number of elements to include per page
      * @see paginate
      */
-    public $elementsPerPage = 100;
+    public int $elementsPerPage = 100;
 
     /**
      * @var string The query string param name that should be used to specify the page number
      * @see paginate
      */
-    public $pageParam = 'page';
+    public string $pageParam = 'page';
 
     /**
      * @var string|null The resource key that should be set on the resource
      */
-    public $resourceKey;
+    public ?string $resourceKey = 'data';
 
     /**
      * @var array|null Custom meta values
      */
-    public $meta;
+    public ?array $meta = null;
 
     /**
      * @inheritdoc
@@ -91,9 +91,9 @@ public function __construct(array $config = [])
      * @inheritdoc
      * @throws InvalidConfigException
      */
-    public function init()
+    public function init(): void
     {
-        if ($this->elementType === null || !is_subclass_of($this->elementType, ElementInterface::class)) {
+        if (!isset($this->elementType) || !is_subclass_of($this->elementType, ElementInterface::class)) {
             throw new InvalidConfigException('Endpoint has an invalid elementType');
         }