diff --git a/lib/AuditLogs.php b/lib/AuditLogs.php
index c453d39..65d7c12 100644
--- a/lib/AuditLogs.php
+++ b/lib/AuditLogs.php
@@ -39,7 +39,7 @@ class AuditLogs
      *
      * @return Resource\AuditLogCreateEventStatus
      */
-    public function createEvent($organizationId, $event, $idempotencyKey = null)
+    public function createEvent($organizationId, $event, ?string $idempotencyKey = null)
     {
         $eventsPath = "audit_logs/events";
 
@@ -73,7 +73,7 @@ public function createEvent($organizationId, $event, $idempotencyKey = null)
      * @return Resource\AuditLogExport
      */
 
-    public function createExport($organizationId, $rangeStart, $rangeEnd, $actions = null, $actors = null, $targets = null, $actorNames = null, $actorIds = null)
+    public function createExport($organizationId, $rangeStart, $rangeEnd, ?array $actions = null, ?array $actors = null, ?array $targets = null, ?array $actorNames = null, ?array $actorIds = null)
     {
         $createExportPath = "audit_logs/exports";
 
diff --git a/lib/Client.php b/lib/Client.php
index d50352b..ea5c6ff 100644
--- a/lib/Client.php
+++ b/lib/Client.php
@@ -46,7 +46,7 @@ public static function setRequestClient($requestClient)
      *
      * @return array<string, mixed>
      */
-    public static function request($method, $path, $headers = null, $params = null, $withAuth = false)
+    public static function request($method, $path, ?array $headers = null, ?array $params = null, $withAuth = false)
     {
         $url = self::generateUrl($path);
 
@@ -105,7 +105,7 @@ public static function generateBaseHeaders($withAuth = false)
      *
      * @return string
      */
-    public static function generateUrl($path, $params = null)
+    public static function generateUrl($path, ?array $params = null)
     {
         $url = WorkOS::getApiBaseUrl() . $path;
 
diff --git a/lib/DirectorySync.php b/lib/DirectorySync.php
index 4fa5671..a065880 100644
--- a/lib/DirectorySync.php
+++ b/lib/DirectorySync.php
@@ -27,13 +27,13 @@ class DirectorySync
      * @return array{?string, ?string, Resource\Directory[]} An array containing the Directory ID to use as before and after cursor, and an array of Directory instances
      */
     public function listDirectories(
-        $domain = null,
-        $search = null,
+        ?string $domain = null,
+        ?string $search = null,
         $limit = self::DEFAULT_PAGE_SIZE,
-        $before = null,
-        $after = null,
-        $organizationId = null,
-        $order = null
+        ?string $before = null,
+        ?string $after = null,
+        ?string $organizationId = null,
+        ?string $order = null
     ) {
         $directoriesPath = "directories";
         $params = [
@@ -78,12 +78,12 @@ public function listDirectories(
      * @return array{?string, ?string, Resource\DirectoryGroup[]} An array containing the Directory Group ID to use as before and after cursor, and an array of Directory Group instances
      */
     public function listGroups(
-        $directory = null,
-        $user = null,
+        ?string $directory = null,
+        ?string $user = null,
         $limit = self::DEFAULT_PAGE_SIZE,
-        $before = null,
-        $after = null,
-        $order = null
+        ?string $before = null,
+        ?string $after = null,
+        ?string $order = null
     ) {
         $groupsPath = "directory_groups";
 
@@ -156,12 +156,12 @@ public function getGroup($directoryGroup)
      * @throws Exception\WorkOSException
      */
     public function listUsers(
-        $directory = null,
-        $group = null,
+        ?string $directory = null,
+        ?string $group = null,
         $limit = self::DEFAULT_PAGE_SIZE,
-        $before = null,
-        $after = null,
-        $order = null
+        ?string $before = null,
+        ?string $after = null,
+        ?string $order = null
     ) {
         $usersPath = "directory_users";
 
diff --git a/lib/Exception/BaseRequestException.php b/lib/Exception/BaseRequestException.php
index ae26f6d..7bcac60 100644
--- a/lib/Exception/BaseRequestException.php
+++ b/lib/Exception/BaseRequestException.php
@@ -25,7 +25,7 @@ class BaseRequestException extends \Exception implements WorkOSException
      * @param Response $response
      * @param null|string $message Exception message
      */
-    public function __construct($response, $message = null)
+    public function __construct($response, ?string $message = null)
     {
         $this->response = $response;
 
diff --git a/lib/Exception/GenericException.php b/lib/Exception/GenericException.php
index 481de48..c84658f 100644
--- a/lib/Exception/GenericException.php
+++ b/lib/Exception/GenericException.php
@@ -17,7 +17,7 @@ class GenericException extends \Exception implements WorkOSException
      * @param string $message Exception message
      * @param null|array $data Blob
      */
-    public function __construct($message, $data = null)
+    public function __construct($message, ?array $data = null)
     {
         $this->message = $message;
 
diff --git a/lib/MFA.php b/lib/MFA.php
index abdb358..5f65372 100644
--- a/lib/MFA.php
+++ b/lib/MFA.php
@@ -21,9 +21,9 @@ class MFA
      */
     public function enrollFactor(
         $type,
-        $totpIssuer = null,
-        $totpUser = null,
-        $phoneNumber = null
+        ?string $totpIssuer = null,
+        ?string $totpUser = null,
+        ?string $phoneNumber = null
     ) {
         $enrollPath = "auth/factors/enroll";
 
@@ -79,7 +79,7 @@ public function enrollFactor(
      */
     public function challengeFactor(
         $authenticationFactorId,
-        $smsTemplate = null
+        ?string $smsTemplate = null
     ) {
         if (!isset($authenticationFactorId)) {
             $msg = "Incomplete arguments: 'authentication_factor_id' is a required parameter";
diff --git a/lib/Organizations.php b/lib/Organizations.php
index 283be2e..d0922a5 100644
--- a/lib/Organizations.php
+++ b/lib/Organizations.php
@@ -26,11 +26,11 @@ class Organizations
      * @throws Exception\WorkOSException
      */
     public function listOrganizations(
-        $domains = null,
+        ?array $domains = null,
         $limit = self::DEFAULT_PAGE_SIZE,
-        $before = null,
-        $after = null,
-        $order = null
+        ?string $before = null,
+        ?string $after = null,
+        ?string $order = null
     ) {
         $organizationsPath = "organizations";
         $params = [
@@ -76,12 +76,12 @@ public function listOrganizations(
      */
     public function createOrganization(
         $name,
-        $domains = null,
-        $allowProfilesOutsideOrganization = null,
-        $idempotencyKey = null,
-        $domain_data = null,
-        $externalId = null,
-        $metadata = null
+        ?array $domains = null,
+        ?bool $allowProfilesOutsideOrganization = null,
+        ?string $idempotencyKey = null,
+        ?array $domain_data = null,
+        ?string $externalId = null,
+        ?array $metadata = null
     ) {
         $idempotencyKey ? $headers = array("Idempotency-Key: $idempotencyKey") : $headers = null;
         $organizationsPath = "organizations";
@@ -126,13 +126,13 @@ public function createOrganization(
      */
     public function updateOrganization(
         $organization,
-        $domains = null,
-        $name = null,
-        $allowProfilesOutsideOrganization = null,
-        $domain_data = null,
-        $stripeCustomerId = null,
-        $externalId = null,
-        $metadata = null
+        ?array $domains = null,
+        ?string $name = null,
+        ?bool $allowProfilesOutsideOrganization = null,
+        ?array $domain_data = null,
+        ?string $stripeCustomerId = null,
+        ?string $externalId = null,
+        ?array $metadata = null
     ) {
         $organizationsPath = "organizations/{$organization}";
 
diff --git a/lib/Portal.php b/lib/Portal.php
index 3364aa9..c361b2a 100644
--- a/lib/Portal.php
+++ b/lib/Portal.php
@@ -23,7 +23,7 @@ class Portal
      *
      * @return Resource\PortalLink
      */
-    public function generateLink($organization, $intent, $returnUrl = null, $successUrl = null)
+    public function generateLink($organization, $intent, ?string $returnUrl = null, ?string $successUrl = null)
     {
         $generateLinkPath = "portal/generate_link";
         $params = [
diff --git a/lib/RequestClient/CurlRequestClient.php b/lib/RequestClient/CurlRequestClient.php
index 5edb6db..b5b9115 100644
--- a/lib/RequestClient/CurlRequestClient.php
+++ b/lib/RequestClient/CurlRequestClient.php
@@ -20,7 +20,7 @@ class CurlRequestClient implements RequestClientInterface
      *
      * @return array An array composed of the result string, response headers and status code
      */
-    public function request($method, $url, $headers = null, $params = null)
+    public function request($method, $url, ?array $headers = null, ?array $params = null)
     {
         if (empty($headers)) {
             $headers = array();
diff --git a/lib/RequestClient/RequestClientInterface.php b/lib/RequestClient/RequestClientInterface.php
index b2fe0dd..a140240 100644
--- a/lib/RequestClient/RequestClientInterface.php
+++ b/lib/RequestClient/RequestClientInterface.php
@@ -19,5 +19,5 @@ interface RequestClientInterface
      *
      * @return array An array composed of the result string, response headers and status code
      */
-    public function request($method, $url, $headers, $params);
+    public function request($method, $url, ?array $headers = null, ?array $params = null);
 }
diff --git a/lib/Resource/WebhookResponse.php b/lib/Resource/WebhookResponse.php
index 3f2032c..8731a82 100644
--- a/lib/Resource/WebhookResponse.php
+++ b/lib/Resource/WebhookResponse.php
@@ -41,7 +41,7 @@ class WebhookResponse
      * @return self
      * @throws \InvalidArgumentException
      */
-    public static function create($type, $secret, $verdict, $errorMessage = null)
+    public static function create($type, $secret, $verdict, ?string $errorMessage = null)
     {
         if (!in_array($type, [self::USER_REGISTRATION_ACTION, self::AUTHENTICATION_ACTION])) {
             throw new \InvalidArgumentException('Invalid response type');
diff --git a/lib/SSO.php b/lib/SSO.php
index 6eed387..dcc57a4 100644
--- a/lib/SSO.php
+++ b/lib/SSO.php
@@ -33,9 +33,9 @@ public function getAuthorizationUrl(
         $state,
         $provider = null,
         $connection = null,
-        $organization = null,
-        $domainHint = null,
-        $loginHint = null
+        ?string $organization = null,
+        ?string $domainHint = null,
+        ?string $loginHint = null
     ) {
         $authorizationPath = "sso/authorize";
 
@@ -219,13 +219,13 @@ public function getConnection($connection)
      * @throws Exception\WorkOSException
      */
     public function listConnections(
-        $domain = null,
-        $connectionType = null,
-        $organizationId = null,
+        ?string $domain = null,
+        ?string $connectionType = null,
+        ?string $organizationId = null,
         $limit = self::DEFAULT_PAGE_SIZE,
-        $before = null,
-        $after = null,
-        $order = null
+        ?string $before = null,
+        ?string $after = null,
+        ?string $order = null
     ) {
         $connectionsPath = "connections";
         $params = [
diff --git a/lib/UserManagement.php b/lib/UserManagement.php
index a277fb1..6045ab9 100644
--- a/lib/UserManagement.php
+++ b/lib/UserManagement.php
@@ -36,14 +36,14 @@ class UserManagement
 
     public function createUser(
         $email,
-        $password = null,
-        $firstName = null,
-        $lastName = null,
-        $emailVerified = null,
-        $passwordHash = null,
-        $passwordHashType = null,
-        $externalId = null,
-        $metadata = null
+        ?string $password = null,
+        ?string $firstName = null,
+        ?string $lastName = null,
+        ?bool $emailVerified = null,
+        ?string $passwordHash = null,
+        ?string $passwordHashType = null,
+        ?string $externalId = null,
+        ?array $metadata = null
     ) {
         $path = "user_management/users";
         $params = [
@@ -119,15 +119,15 @@ public function getUserByExternalId($externalId)
      */
     public function updateUser(
         $userId,
-        $firstName = null,
-        $lastName = null,
-        $emailVerified = null,
-        $password = null,
-        $passwordHash = null,
-        $passwordHashType = null,
-        $externalId = null,
-        $metadata = null,
-        $email = null
+        ?string $firstName = null,
+        ?string $lastName = null,
+        ?bool $emailVerified = null,
+        ?string $password = null,
+        ?string $passwordHash = null,
+        ?string $passwordHashType = null,
+        ?string $externalId = null,
+        ?array $metadata = null,
+        ?string $email = null
     ) {
         $path = "user_management/users/{$userId}";
 
@@ -163,12 +163,12 @@ public function updateUser(
      * @throws Exception\WorkOSException
      */
     public function listUsers(
-        $email = null,
-        $organizationId = null,
+        ?string $email = null,
+        ?string $organizationId = null,
         $limit = self::DEFAULT_PAGE_SIZE,
-        $before = null,
-        $after = null,
-        $order = null
+        ?string $before = null,
+        ?string $after = null,
+        ?string $order = null
     ) {
         $path = "user_management/users";
 
@@ -222,13 +222,13 @@ public function deleteUser($userId)
      * @param string $userId User ID
      * @param string $organizationId Organization ID
      * @param string|null $roleSlug Role Slug
-     * @param string|null $roleSlugs Role Slugs
+     * @param array|null $roleSlugs Role Slugs
      *
      * @throws Exception\WorkOSException
      *
      * @return Resource\OrganizationMembership
      */
-    public function createOrganizationMembership($userId, $organizationId, $roleSlug = null, $roleSlugs = null)
+    public function createOrganizationMembership($userId, $organizationId, ?string $roleSlug = null, ?array $roleSlugs = null)
     {
         $path = "user_management/organization_memberships";
 
@@ -309,13 +309,13 @@ public function deleteOrganizationMembership($organizationMembershipId)
      *
      * @param string $organizationMembershipId Organization Membership ID
      * @param string|null $role_slug The unique slug of the role to grant to this membership.
-     * @param string|null $role_slugs The unique slugs of the roles to grant to this membership.
+     * @param array|null $role_slugs The unique slugs of the roles to grant to this membership.
      *
      * @throws Exception\WorkOSException
      *
      * @return Resource\OrganizationMembership
      */
-    public function updateOrganizationMembership($organizationMembershipId, $roleSlug = null, $roleSlugs = null)
+    public function updateOrganizationMembership($organizationMembershipId, ?string $roleSlug = null, ?array $roleSlugs = null)
     {
         $path = "user_management/organization_memberships/{$organizationMembershipId}";
 
@@ -356,13 +356,13 @@ public function updateOrganizationMembership($organizationMembershipId, $roleSlu
      * @return array{?string, ?string, Resource\OrganizationMembership[]} An array containing the Organization Membership ID to use as before and after cursor, and a list of Organization Memberships instances
      */
     public function listOrganizationMemberships(
-        $userId = null,
-        $organizationId = null,
-        $statuses = null,
+        ?string $userId = null,
+        ?string $organizationId = null,
+        ?array $statuses = null,
         $limit = self::DEFAULT_PAGE_SIZE,
-        $before = null,
-        $after = null,
-        $order = null
+        ?string $before = null,
+        ?string $after = null,
+        ?string $order = null
     ) {
         $path = "user_management/organization_memberships";
 
@@ -467,10 +467,10 @@ public function reactivateOrganizationMembership($organizationMembershipId)
      */
     public function sendInvitation(
         $email,
-        $organizationId = null,
-        $expiresInDays = null,
-        $inviterUserId = null,
-        $roleSlug = null
+        ?string $organizationId = null,
+        ?int $expiresInDays = null,
+        ?string $inviterUserId = null,
+        ?string $roleSlug = null
     ) {
         $path = "user_management/invitations";
 
@@ -556,12 +556,12 @@ public function findInvitationByToken($invitationToken)
      * @return array{?string, ?string, Resource\Invitation[]} An array containing the Invitation ID to use as before and after cursor, and a list of Invitations instances
      */
     public function listInvitations(
-        $email = null,
-        $organizationId = null,
+        ?string $email = null,
+        ?string $organizationId = null,
         $limit = self::DEFAULT_PAGE_SIZE,
-        $before = null,
-        $after = null,
-        $order = null
+        ?string $before = null,
+        ?string $after = null,
+        ?string $order = null
     ) {
         $path = "user_management/invitations";
 
@@ -663,12 +663,12 @@ public function getAuthorizationUrl(
         $redirectUri,
         $state = null,
         $provider = null,
-        $connectionId = null,
-        $organizationId = null,
-        $domainHint = null,
-        $loginHint = null,
-        $screenHint = null,
-        $providerScopes = null
+        ?string $connectionId = null,
+        ?string $organizationId = null,
+        ?string $domainHint = null,
+        ?string $loginHint = null,
+        ?string $screenHint = null,
+        ?array $providerScopes = null
     ) {
         $path = "user_management/authorize";
 
@@ -750,7 +750,7 @@ public function getAuthorizationUrl(
      *
      * @return Resource\AuthenticationResponse
      */
-    public function authenticateWithPassword($clientId, $email, $password, $ipAddress = null, $userAgent = null)
+    public function authenticateWithPassword($clientId, $email, $password, ?string $ipAddress = null, ?string $userAgent = null)
     {
         $path = "user_management/authenticate";
         $params = [
@@ -785,8 +785,8 @@ public function authenticateWithSelectedOrganization(
         $clientId,
         $pendingAuthenticationToken,
         $organizationId,
-        $ipAddress = null,
-        $userAgent = null
+        ?string $ipAddress = null,
+        ?string $userAgent = null
     ) {
         $path = "user_management/authenticate";
         $params = [
@@ -817,7 +817,7 @@ public function authenticateWithSelectedOrganization(
      *
      * @return Resource\AuthenticationResponse
      */
-    public function authenticateWithCode($clientId, $code, $ipAddress = null, $userAgent = null)
+    public function authenticateWithCode($clientId, $code, ?string $ipAddress = null, ?string $userAgent = null)
     {
         $path = "user_management/authenticate";
         $params = [
@@ -847,7 +847,7 @@ public function authenticateWithCode($clientId, $code, $ipAddress = null, $userA
      *
      * @return Resource\AuthenticationResponse
      */
-    public function authenticateWithEmailVerification($clientId, $code, $pendingAuthenticationToken, $ipAddress = null, $userAgent = null)
+    public function authenticateWithEmailVerification($clientId, $code, $pendingAuthenticationToken, ?string $ipAddress = null, ?string $userAgent = null)
     {
         $path = "user_management/authenticate";
         $params = [
@@ -883,8 +883,8 @@ public function authenticateWithMagicAuth(
         $clientId,
         $code,
         $userId,
-        $ipAddress = null,
-        $userAgent = null
+        ?string $ipAddress = null,
+        ?string $userAgent = null
     ) {
         $path = "user_management/authenticate";
         $params = [
@@ -917,9 +917,9 @@ public function authenticateWithMagicAuth(
     public function authenticateWithRefreshToken(
         $clientId,
         $refreshToken,
-        $ipAddress = null,
-        $userAgent = null,
-        $organizationId = null
+        ?string $ipAddress = null,
+        ?string $userAgent = null,
+        ?string $organizationId = null
     ) {
         $path = "user_management/authenticate";
         $params = [
@@ -956,8 +956,8 @@ public function authenticateWithTotp(
         $pendingAuthenticationToken,
         $authenticationChallengeId,
         $code,
-        $ipAddress = null,
-        $userAgent = null
+        ?string $ipAddress = null,
+        ?string $userAgent = null
     ) {
         $path = "user_management/authenticate";
         $params = [
@@ -988,7 +988,7 @@ public function authenticateWithTotp(
      *
      * @return Resource\AuthenticationFactorAndChallengeTotp
      */
-    public function enrollAuthFactor($userId, $type, $totpIssuer = null, $totpUser = null)
+    public function enrollAuthFactor($userId, $type, ?string $totpIssuer = null, ?string $totpUser = null)
     {
         $path = "user_management/users/{$userId}/auth_factors";
 
@@ -1234,7 +1234,7 @@ public function getMagicAuth($magicAuthId)
      */
     public function createMagicAuth(
         $email,
-        $invitationToken = null
+        ?string $invitationToken = null
     ) {
         $path = "user_management/magic_auth";
 
@@ -1315,7 +1315,7 @@ public function getJwksUrl(string $clientId)
      *
      * @return string
      */
-    public function getLogoutUrl(string $sessionId, string $return_to = null)
+    public function getLogoutUrl(string $sessionId, ?string $return_to = null)
     {
         if (!isset($sessionId) || empty($sessionId)) {
             throw new Exception\UnexpectedValueException("sessionId must not be empty");
diff --git a/tests/WorkOS/AuditLogsTest.php b/tests/WorkOS/AuditLogsTest.php
index 54127fc..310cfaa 100644
--- a/tests/WorkOS/AuditLogsTest.php
+++ b/tests/WorkOS/AuditLogsTest.php
@@ -111,6 +111,37 @@ public function testCreateExport()
         $this->assertSame($exportFixture, $auditLogExport->toArray());
     }
 
+    public function testCreateExportWithNullOptionalParams()
+    {
+        $path = "audit_logs/exports";
+
+        $organizationId = "org_123";
+        $rangeStart = "2022-08-18T18:07:10.822Z";
+        $rangeEnd = "2022-08-18T18:07:10.822Z";
+        // The implementation filters out null values, so they won't be in the params array
+        $params = [
+            "organization_id" => $organizationId,
+            "range_end" => $rangeEnd,
+            "range_start" => $rangeStart
+        ];
+
+        $result = $this->createExportResponseFixture();
+
+        $this->mockRequest(
+            Client::METHOD_POST,
+            $path,
+            null,
+            $params,
+            true,
+            $result
+        );
+
+        $auditLogExport = $this->al->createExport($organizationId, $rangeStart, $rangeEnd, null, null, null, null, null);
+        $exportFixture = $this->createExportFixture();
+
+        $this->assertSame($exportFixture, $auditLogExport->toArray());
+    }
+
     public function testGetExport()
     {
         $auditLogExportId = "123";
diff --git a/tests/WorkOS/ClientTest.php b/tests/WorkOS/ClientTest.php
index 3bc6ec7..654ce9b 100644
--- a/tests/WorkOS/ClientTest.php
+++ b/tests/WorkOS/ClientTest.php
@@ -185,6 +185,46 @@ public function testClientThrowsRequestExceptionsWithErrors($statusCode, $except
         }
     }
 
+    public function testClientRequestWithNullHeadersAndParams()
+    {
+        $this->withApiKeyAndClientId();
+
+        $path = "some/place";
+        $result = json_encode(["data" => "test"]);
+
+        // Client::request always generates base headers even when null is passed
+        // When $withAuth is false (default), it still includes User-Agent header
+        $this->mockRequest(
+            Client::METHOD_GET,
+            $path,
+            null,
+            null,
+            false,
+            $result
+        );
+
+        $response = Client::request(Client::METHOD_GET, $path, null, null);
+        $this->assertSame(["data" => "test"], $response);
+    }
+
+    public function testClientGenerateUrl()
+    {
+        $this->withApiKeyAndClientId();
+
+        $path = "test/path";
+        $url = Client::generateUrl($path);
+        $this->assertStringContainsString($path, $url);
+    }
+
+    public function testClientGenerateUrlWithNullParams()
+    {
+        $this->withApiKeyAndClientId();
+
+        $path = "test/path";
+        $url = Client::generateUrl($path, null);
+        $this->assertStringContainsString($path, $url);
+    }
+
     // Providers
     public static function requestExceptionTestProvider()
     {
diff --git a/tests/WorkOS/UserManagementTest.php b/tests/WorkOS/UserManagementTest.php
index cb52713..9326bed 100644
--- a/tests/WorkOS/UserManagementTest.php
+++ b/tests/WorkOS/UserManagementTest.php
@@ -75,6 +75,40 @@ public function testUpdateUser()
         $this->assertSame($user, $response->toArray());
     }
 
+    public function testUpdateUserWithNullOptionalParams()
+    {
+        $userId = "user_01H7X1M4TZJN5N4HG4XXMA1234";
+        $path = "user_management/users/{$userId}";
+
+        $result = $this->createUserResponseFixture();
+
+        $params = [
+            "first_name" => null,
+            "last_name" => null,
+            "email_verified" => null,
+            "password" => null,
+            "password_hash" => null,
+            "password_hash_type" => null,
+            "external_id" => null,
+            "metadata" => null,
+            "email" => null
+        ];
+
+        $this->mockRequest(
+            Client::METHOD_PUT,
+            $path,
+            null,
+            $params,
+            true,
+            $result
+        );
+
+        $user = $this->userFixture();
+
+        $response = $this->userManagement->updateUser("user_01H7X1M4TZJN5N4HG4XXMA1234", null, null, null, null, null, null, null, null, null);
+        $this->assertSame($user, $response->toArray());
+    }
+
     public function testAuthorizationURLInvalidInputs()
     {
         $this->expectException(Exception\UnexpectedValueException::class);
@@ -423,6 +457,35 @@ public function testEnrollAuthFactor()
         $this->assertSame($enrollUserAuthChallengeFixture, $enrollFactorTotp->authenticationChallenge->toArray());
     }
 
+    public function testEnrollAuthFactorWithNullOptionalParams()
+    {
+        $userId = "user_123456";
+        $path = "user_management/users/{$userId}/auth_factors";
+        $params = [
+            "type" => "totp",
+            "totp_user" => null,
+            "totp_issuer" => null
+        ];
+
+        $result = $this->enrollAuthFactorResponseFixture();
+
+        $this->mockRequest(
+            Client::METHOD_POST,
+            $path,
+            null,
+            $params,
+            true,
+            $result
+        );
+
+        $enrollFactorTotp = $this->userManagement->enrollAuthFactor($userId, "totp", null, null);
+        $enrollUserAuthFactorFixture = $this->enrollAuthFactorFixture();
+        $enrollUserAuthChallengeFixture = $this->enrollAuthChallengeFixture();
+
+        $this->assertSame($enrollUserAuthFactorFixture, $enrollFactorTotp->authenticationFactor->toArray());
+        $this->assertSame($enrollUserAuthChallengeFixture, $enrollFactorTotp->authenticationChallenge->toArray());
+    }
+
     public function testAuthenticateWithRefreshToken()
     {
         $path = "user_management/authenticate";
@@ -550,6 +613,39 @@ public function testCreateUser()
         $this->assertSame($user, $response->toArray());
     }
 
+    public function testCreateUserWithNullOptionalParams()
+    {
+        $path = "user_management/users";
+
+        $result = $this->createUserResponseFixture();
+
+        $params = [
+            "email" => "test@test.com",
+            "password" => null,
+            "first_name" => null,
+            "last_name" => null,
+            "email_verified" => null,
+            "password_hash" => null,
+            "password_hash_type" => null,
+            "external_id" => null,
+            "metadata" => null
+        ];
+
+        $this->mockRequest(
+            Client::METHOD_POST,
+            $path,
+            null,
+            $params,
+            true,
+            $result
+        );
+
+        $user = $this->userFixture();
+
+        $response = $this->userManagement->createUser("test@test.com", null, null, null, null, null, null, null, null);
+        $this->assertSame($user, $response->toArray());
+    }
+
     public function testGetEmailVerification()
     {
         $emailVerificationId = "email_verification_01E4ZCR3C56J083X43JQXF3JK5";
@@ -943,6 +1039,35 @@ public function testCreateOrganizationMembershipWithRoleSlugs()
         $this->assertSame($organizationMembership, $response->toArray());
     }
 
+    public function testCreateOrganizationMembershipWithNullRoleParams()
+    {
+        $userId = "user_01H7X1M4TZJN5N4HG4XXMA1234";
+        $orgId = "org_01EHQMYV6MBK39QC5PZXHY59C3";
+        $path = "user_management/organization_memberships";
+
+        $result = $this->organizationMembershipResponseFixture();
+
+        // When both roleSlug and roleSlugs are null, neither should be in params
+        $params = [
+            "organization_id" => $orgId,
+            "user_id" => $userId,
+        ];
+
+        $this->mockRequest(
+            Client::METHOD_POST,
+            $path,
+            null,
+            $params,
+            true,
+            $result
+        );
+
+        $organizationMembership = $this->organizationMembershipFixture();
+
+        $response = $this->userManagement->createOrganizationMembership($userId, $orgId, null, null);
+        $this->assertSame($organizationMembership, $response->toArray());
+    }
+
     public function testGetOrganizationMembership()
     {
         $organizationMembershipId = "om_01E4ZCR3C56J083X43JQXF3JK5";
@@ -1132,6 +1257,26 @@ public function testUpdateOrganizationMembershipWithRoleSlugs()
         $this->assertSame($this->organizationMembershipFixture(), $response->toArray());
     }
 
+    public function testUpdateOrganizationMembershipWithNullRoleParams()
+    {
+        $organizationMembershipId = "om_01E4ZCR3C56J083X43JQXF3JK5";
+        $path = "user_management/organization_memberships/{$organizationMembershipId}";
+
+        $result = $this->organizationMembershipResponseFixture();
+
+        // When both roleSlug and roleSlugs are null, params should be empty array
+        $this->mockRequest(
+            Client::METHOD_PUT,
+            $path,
+            null,
+            [],
+            true,
+            $result
+        );
+
+        $response = $this->userManagement->updateOrganizationMembership($organizationMembershipId, null, null);
+        $this->assertSame($this->organizationMembershipFixture(), $response->toArray());
+    }
 
     public function testDeactivateOrganizationMembership()
     {
@@ -1215,6 +1360,43 @@ public function testSendInvitation()
         $this->assertSame($response->toArray(), $expected);
     }
 
+    public function testSendInvitationWithNullOptionalParams()
+    {
+        $path = "user_management/invitations";
+
+        $result = $this->invitationResponseFixture();
+
+        // The implementation includes null values in params
+        $params = [
+            "email" => "someemail@test.com",
+            "organization_id" => null,
+            "expires_in_days" => null,
+            "inviter_user_id" => null,
+            "role_slug" => null
+        ];
+
+        $this->mockRequest(
+            Client::METHOD_POST,
+            $path,
+            null,
+            $params,
+            true,
+            $result
+        );
+
+        $response = $this->userManagement->sendInvitation(
+            "someemail@test.com",
+            null,
+            null,
+            null,
+            null
+        );
+
+        $expected = $this->invitationFixture();
+
+        $this->assertSame($response->toArray(), $expected);
+    }
+
     public function testGetInvitation()
     {
         $invitationId = "invitation_01E4ZCR3C56J083X43JQXF3JK5";