diff --git a/CHANGELOG.md b/CHANGELOG.md
index fd78e7b6..8cdbbaa3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Deprecated
 ### Removed
 ### Fixed
+- Fixed upcomming PHP 8.4 deprecations
 ### Updated APIs
 - Updated opensearch-php APIs to reflect [opensearch-api-specification@cb320b5](https://github.com/opensearch-project/opensearch-api-specification/commit/cb320b5482551c4f28afa26ff0d1653332699722)
 ### Security
diff --git a/src/OpenSearch/ClientBuilder.php b/src/OpenSearch/ClientBuilder.php
index 20c6b7af..1865bc3d 100644
--- a/src/OpenSearch/ClientBuilder.php
+++ b/src/OpenSearch/ClientBuilder.php
@@ -531,7 +531,7 @@ public function setSniffOnStart(bool $sniffOnStart): 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];
 
@@ -544,7 +544,7 @@ public function setSSLCert(string $cert, string $password = null): 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];
 
diff --git a/src/OpenSearch/Common/Exceptions/Serializer/JsonErrorException.php b/src/OpenSearch/Common/Exceptions/Serializer/JsonErrorException.php
index 2456ae8c..db2de9ad 100644
--- a/src/OpenSearch/Common/Exceptions/Serializer/JsonErrorException.php
+++ b/src/OpenSearch/Common/Exceptions/Serializer/JsonErrorException.php
@@ -60,7 +60,7 @@ class JsonErrorException extends \Exception implements OpenSearchException
      * @param mixed $input
      * @param mixed $result
      */
-    public function __construct(int $code, $input, $result, \Throwable $previous = null)
+    public function __construct(int $code, $input, $result, ?\Throwable $previous = null)
     {
         if (isset(self::$messages[$code]) !== true) {
             throw new \InvalidArgumentException(sprintf('Encountered unknown JSON error code: [%d]', $code));
diff --git a/src/OpenSearch/Connections/Connection.php b/src/OpenSearch/Connections/Connection.php
index c81861f8..7279f56c 100644
--- a/src/OpenSearch/Connections/Connection.php
+++ b/src/OpenSearch/Connections/Connection.php
@@ -202,7 +202,7 @@ public function __construct(
      * @param  Transport|null $transport
      * @return mixed
      */
-    public function performRequest(string $method, string $uri, ?array $params = [], $body = null, array $options = [], Transport $transport = null)
+    public function performRequest(string $method, string $uri, ?array $params = [], $body = null, array $options = [], ?Transport $transport = null)
     {
         if ($body !== null) {
             $body = $this->serializer->serialize($body);
@@ -256,7 +256,7 @@ public function getLastRequestInfo(): array
 
     private function wrapHandler(callable $handler): callable
     {
-        return function (array $request, Connection $connection, Transport $transport = null, $options) use ($handler) {
+        return function (array $request, Connection $connection, ?Transport $transport, $options) use ($handler) {
             $this->lastRequest = [];
             $this->lastRequest['request'] = $request;
 
diff --git a/src/OpenSearch/Connections/ConnectionInterface.php b/src/OpenSearch/Connections/ConnectionInterface.php
index 0a5adcf5..0e6280ae 100644
--- a/src/OpenSearch/Connections/ConnectionInterface.php
+++ b/src/OpenSearch/Connections/ConnectionInterface.php
@@ -79,5 +79,5 @@ public function getLastRequestInfo(): array;
      * @param  mixed $body
      * @return mixed
      */
-    public function performRequest(string $method, string $uri, ?array $params = [], $body = null, array $options = [], Transport $transport = null);
+    public function performRequest(string $method, string $uri, ?array $params = [], $body = null, array $options = [], ?Transport $transport = null);
 }
diff --git a/src/OpenSearch/Handlers/SigV4Handler.php b/src/OpenSearch/Handlers/SigV4Handler.php
index b40613b4..e45639c7 100644
--- a/src/OpenSearch/Handlers/SigV4Handler.php
+++ b/src/OpenSearch/Handlers/SigV4Handler.php
@@ -47,8 +47,8 @@ class SigV4Handler
     public function __construct(
         string $region,
         string $service,
-        callable $credentialProvider = null,
-        callable $wrappedHandler = null
+        ?callable $credentialProvider = null,
+        ?callable $wrappedHandler = null
     ) {
         self::assertDependenciesInstalled();
         $this->signer = new SignatureV4($service, $region);