diff --git a/lib/UserManagement.php b/lib/UserManagement.php
index e21eae6a..eae733a2 100644
--- a/lib/UserManagement.php
+++ b/lib/UserManagement.php
@@ -218,18 +218,20 @@ public function deleteUser($userId)
      *
      * @param string $userId User ID
      * @param string $organizationId Organization ID
+     * @param string|null $roleSlug Role Slug
      *
      * @throws Exception\WorkOSException
      *
      * @return Resource\OrganizationMembership
      */
-    public function createOrganizationMembership($userId, $organizationId)
+    public function createOrganizationMembership($userId, $organizationId, $roleSlug = null)
     {
         $path = "user_management/organization_memberships";
 
         $params = [
             "organization_id" => $organizationId,
-            "user_id" => $userId
+            "user_id" => $userId,
+            "role_slug" => $roleSlug
         ];
 
         $response = Client::request(
@@ -295,18 +297,18 @@ public function deleteOrganizationMembership($organizationMembershipId)
      * Update a User organization membership.
      *
      * @param string $organizationMembershipId Organization Membership ID
-     * @param string $role_slug The unique role identifier.
+     * @param string|null $role_slug The unique role identifier.
      *
      * @throws Exception\WorkOSException
      *
      * @return Resource\OrganizationMembership
      */
-    public function updateOrganizationMembership($organizationMembershipId, $role_slug)
+    public function updateOrganizationMembership($organizationMembershipId, $roleSlug = null)
     {
         $path = "user_management/organization_memberships/{$organizationMembershipId}";
 
         $params = [
-            "role_slug" => $role_slug
+            "role_slug" => $roleSlug
         ];
 
         $response = Client::request(
diff --git a/tests/WorkOS/UserManagementTest.php b/tests/WorkOS/UserManagementTest.php
index 9a2b74aa..83b81063 100644
--- a/tests/WorkOS/UserManagementTest.php
+++ b/tests/WorkOS/UserManagementTest.php
@@ -837,13 +837,15 @@ public function testCreateOrganizationMembership()
     {
         $userId = "user_01H7X1M4TZJN5N4HG4XXMA1234";
         $orgId = "org_01EHQMYV6MBK39QC5PZXHY59C3";
+        $roleSlug = "admin";
         $path = "user_management/organization_memberships";
 
         $result = $this->organizationMembershipResponseFixture();
 
         $params = [
             "organization_id" => $orgId,
-            "user_id" => $userId
+            "user_id" => $userId,
+            "role_slug" => $roleSlug
         ];
 
         $this->mockRequest(
@@ -857,7 +859,8 @@ public function testCreateOrganizationMembership()
 
         $organizationMembership = $this->organizationMembershipFixture();
 
-        $response = $this->userManagement->createOrganizationMembership($userId, $orgId);
+        $response = $this->userManagement->createOrganizationMembership($userId, $orgId, $roleSlug);
+
         $this->assertSame($organizationMembership, $response->toArray());
     }