diff --git a/.github/workflows/coding-standards.yml b/.github/workflows/coding-standards.yml
index 408107d..29ef794 100644
--- a/.github/workflows/coding-standards.yml
+++ b/.github/workflows/coding-standards.yml
@@ -33,7 +33,7 @@ jobs:
           COMPOSER_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
       - name: "Install dependencies with Composer"
-        uses: "ramsey/composer-install@v2"
+        uses: "ramsey/composer-install@v3"
 
       - name: "Run PHP CS Fixer"
         run: "vendor/bin/php-cs-fixer fix --verbose --dry-run"
diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index d612d44..d267576 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -42,7 +42,7 @@ jobs:
           COMPOSER_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
       - name: "Install dependencies with Composer"
-        uses: "ramsey/composer-install@v2"
+        uses: "ramsey/composer-install@v3"
 
       - name: "Run PHPUnit"
         run: "php vendor/bin/simple-phpunit -v"
@@ -74,7 +74,7 @@ jobs:
           COMPOSER_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
       - name: "Install dependencies with Composer"
-        uses: "ramsey/composer-install@v2"
+        uses: "ramsey/composer-install@v3"
 
       - name: "Setup logs"
         run: "mkdir -p build/logs"
diff --git a/lib/Imgur/Api/AbstractApi.php b/lib/Imgur/Api/AbstractApi.php
index fbf7120..bdc1a55 100644
--- a/lib/Imgur/Api/AbstractApi.php
+++ b/lib/Imgur/Api/AbstractApi.php
@@ -23,7 +23,7 @@ abstract class AbstractApi
      */
     protected $pager;
 
-    public function __construct(Client $client, PagerInterface $pager = null)
+    public function __construct(Client $client, ?PagerInterface $pager = null)
     {
         $this->client = $client;
         $this->pager = $pager;
diff --git a/lib/Imgur/Auth/AuthInterface.php b/lib/Imgur/Auth/AuthInterface.php
index 79fda82..a109ff5 100644
--- a/lib/Imgur/Auth/AuthInterface.php
+++ b/lib/Imgur/Auth/AuthInterface.php
@@ -15,11 +15,11 @@ interface AuthInterface
      * @param string $responseType (code, token, pin) Determines if Imgur should return an authorization_code, a PIN code, or an opaque access_token
      * @param string $state        Any value which you want Imgur to pass back
      */
-    public function getAuthenticationUrl(string $responseType = 'code', string $state = null): string;
+    public function getAuthenticationUrl(string $responseType = 'code', ?string $state = null): string;
 
     public function getAccessToken(): ?array;
 
-    public function requestAccessToken(string $code, string $requestType = null): array;
+    public function requestAccessToken(string $code, ?string $requestType = null): array;
 
     public function setAccessToken(array $accessToken): void;
 
diff --git a/lib/Imgur/Auth/OAuth2.php b/lib/Imgur/Auth/OAuth2.php
index d6142db..b5e07ed 100644
--- a/lib/Imgur/Auth/OAuth2.php
+++ b/lib/Imgur/Auth/OAuth2.php
@@ -72,7 +72,7 @@ public function __construct(HttpClientInterface $httpClient, string $clientId, s
     /**
      * Generates the authentication URL to which a user should be pointed at in order to start the OAuth2 process.
      */
-    public function getAuthenticationURL(string $responseType = 'code', string $state = null): string
+    public function getAuthenticationURL(string $responseType = 'code', ?string $state = null): string
     {
         $httpQueryParameters = [
             'client_id' => $this->clientId,
@@ -88,7 +88,7 @@ public function getAuthenticationURL(string $responseType = 'code', string $stat
     /**
      * Exchanges a code/pin for an access token.
      */
-    public function requestAccessToken(string $code, string $requestType = null): array
+    public function requestAccessToken(string $code, ?string $requestType = null): array
     {
         switch ($requestType) {
             case 'pin':
@@ -166,7 +166,7 @@ public function refreshToken(): array
      *
      * @throws AuthException
      */
-    public function setAccessToken(array $token = null): void
+    public function setAccessToken(?array $token = null): void
     {
         if (!\is_array($token)) {
             throw new AuthException('Token is not a valid json string.');
diff --git a/lib/Imgur/Client.php b/lib/Imgur/Client.php
index 2384180..a454dd8 100644
--- a/lib/Imgur/Client.php
+++ b/lib/Imgur/Client.php
@@ -42,7 +42,7 @@ class Client
      *
      * @param HttpClientInterface|null $httpClient Imgur http client
      */
-    public function __construct(AuthInterface $authenticationClient = null, HttpClientInterface $httpClient = null)
+    public function __construct(?AuthInterface $authenticationClient = null, ?HttpClientInterface $httpClient = null)
     {
         $this->httpClient = $httpClient;
         $this->authenticationClient = $authenticationClient;
@@ -51,7 +51,7 @@ public function __construct(AuthInterface $authenticationClient = null, HttpClie
     /**
      * @throws InvalidArgumentException
      */
-    public function api(string $name, PagerInterface $pager = null): AbstractApi
+    public function api(string $name, ?PagerInterface $pager = null): AbstractApi
     {
         if (!$this->getAccessToken()) {
             $this->sign();
@@ -97,7 +97,7 @@ public function getOption(string $name): ?string
     /**
      * @throws InvalidArgumentException
      */
-    public function setOption(string $name, string $value = null): void
+    public function setOption(string $name, ?string $value = null): void
     {
         if (!\array_key_exists($name, $this->options)) {
             throw new InvalidArgumentException(sprintf('Undefined option called: "%s"', $name));
@@ -125,7 +125,7 @@ public function getAuthenticationClient(): AuthInterface
     /**
      * Proxy method for the authentication objects URL building method.
      */
-    public function getAuthenticationUrl(string $responseType = 'code', string $state = null): string
+    public function getAuthenticationUrl(string $responseType = 'code', ?string $state = null): string
     {
         return $this->getAuthenticationClient()->getAuthenticationUrl($responseType, $state);
     }
diff --git a/lib/Imgur/HttpClient/HttpClient.php b/lib/Imgur/HttpClient/HttpClient.php
index f9f0daa..d21f5f8 100644
--- a/lib/Imgur/HttpClient/HttpClient.php
+++ b/lib/Imgur/HttpClient/HttpClient.php
@@ -37,7 +37,7 @@ class HttpClient implements HttpClientInterface
     /** @var HandlerStack */
     protected $stack;
 
-    public function __construct(array $options = [], ClientInterface $client = null, HandlerStack $stack = null)
+    public function __construct(array $options = [], ?ClientInterface $client = null, ?HandlerStack $stack = null)
     {
         $this->options = array_merge($options, $this->options);
 
diff --git a/tests/HttpClient/HttpClientTest.php b/tests/HttpClient/HttpClientTest.php
index 7782250..5ae2cc9 100644
--- a/tests/HttpClient/HttpClientTest.php
+++ b/tests/HttpClient/HttpClientTest.php
@@ -292,7 +292,7 @@ class TestHttpClient extends HttpClient
     /**
      * @return array|string|null
      */
-    public function getOption(string $name, string $default = null)
+    public function getOption(string $name, ?string $default = null)
     {
         return $this->options[$name] ?? $default;
     }