diff --git a/src/workos/types/user_management/organization_membership.py b/src/workos/types/user_management/organization_membership.py
index 0f944070..2d00b839 100644
--- a/src/workos/types/user_management/organization_membership.py
+++ b/src/workos/types/user_management/organization_membership.py
@@ -1,4 +1,4 @@
-from typing import Literal, Sequence, Optional
+from typing import Any, Dict, Literal, Sequence, Optional
 from typing_extensions import TypedDict
 
 from workos.types.workos_model import WorkOSModel
@@ -21,5 +21,6 @@ class OrganizationMembership(WorkOSModel):
     role: OrganizationMembershipRole
     roles: Optional[Sequence[OrganizationMembershipRole]] = None
     status: LiteralOrUntyped[OrganizationMembershipStatus]
+    custom_attributes: Dict[str, Any]
     created_at: str
     updated_at: str
diff --git a/tests/utils/fixtures/mock_organization_membership.py b/tests/utils/fixtures/mock_organization_membership.py
index bc2ea29c..b363b48b 100644
--- a/tests/utils/fixtures/mock_organization_membership.py
+++ b/tests/utils/fixtures/mock_organization_membership.py
@@ -13,6 +13,7 @@ def __init__(self, id):
             organization_id="org_67890",
             status="active",
             role={"slug": "member"},
+            custom_attributes={},
             created_at=now,
             updated_at=now,
         )