diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 822de1841..e1cb77e61 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -9,7 +9,7 @@ jobs:
 
     strategy:
       matrix:
-        php-version: [7.4, 8.0, 8.1, 8.2, 8.3]
+        php-version: [7.4, 8.0, 8.1, 8.2, 8.3, 8.4]
         os: [ubuntu-latest]
         es-version: [8.14-SNAPSHOT]
 
diff --git a/src/ClientBuilder.php b/src/ClientBuilder.php
index 0d05e1bdf..cf4f2ca94 100644
--- a/src/ClientBuilder.php
+++ b/src/ClientBuilder.php
@@ -226,7 +226,7 @@ public function setHosts(array $hosts): ClientBuilder
      *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-create-api-key.html
      */
-    public function setApiKey(string $apiKey, string $id = null): ClientBuilder
+    public function setApiKey(string $apiKey, ?string $id = null): ClientBuilder
     {
         if (empty($id)) {
             $this->apiKey = $apiKey;
@@ -272,7 +272,7 @@ public function setRetries(int $retries): ClientBuilder
      * @param string $cert The name of a file containing a PEM formatted certificate
      * @param string $password if the certificate requires a password
      */
-    public function setSSLCert(string $cert, string $password = null): ClientBuilder
+    public function setSSLCert(string $cert, ?string $password = null): ClientBuilder
     {
         $this->sslCert = [$cert, $password];
         return $this;
@@ -295,7 +295,7 @@ public function setCABundle(string $cert): ClientBuilder
      * @param string $key The name of a file containing a private SSL key
      * @param string $password if the private key requires a password
      */
-    public function setSSLKey(string $key, string $password = null): ClientBuilder
+    public function setSSLKey(string $key, ?string $password = null): ClientBuilder
     {
         $this->sslKey = [$key, $password];
         return $this;
@@ -469,4 +469,4 @@ protected function setOptions(ClientInterface $client, array $config, array $cli
         $adapter = new $adapterClass;
         return $adapter->setConfig($client, $config, $clientOptions);
     }
-}
\ No newline at end of file
+}