diff --git a/slack_sdk/web/async_client.py b/slack_sdk/web/async_client.py
index 44aa8783..f9a31428 100644
--- a/slack_sdk/web/async_client.py
+++ b/slack_sdk/web/async_client.py
@@ -1730,7 +1730,7 @@ async def admin_users_invite(
     async def admin_users_list(
         self,
         *,
-        team_id: str,
+        team_id: Optional[str] = None,
         include_deactivated_user_workspaces: Optional[bool] = None,
         is_active: Optional[bool] = None,
         cursor: Optional[str] = None,
diff --git a/slack_sdk/web/client.py b/slack_sdk/web/client.py
index b0362136..1747e0d4 100644
--- a/slack_sdk/web/client.py
+++ b/slack_sdk/web/client.py
@@ -1720,7 +1720,7 @@ def admin_users_invite(
     def admin_users_list(
         self,
         *,
-        team_id: str,
+        team_id: Optional[str] = None,
         include_deactivated_user_workspaces: Optional[bool] = None,
         is_active: Optional[bool] = None,
         cursor: Optional[str] = None,
diff --git a/slack_sdk/web/legacy_client.py b/slack_sdk/web/legacy_client.py
index 6bb8a815..ed217764 100644
--- a/slack_sdk/web/legacy_client.py
+++ b/slack_sdk/web/legacy_client.py
@@ -1732,7 +1732,7 @@ def admin_users_invite(
     def admin_users_list(
         self,
         *,
-        team_id: str,
+        team_id: Optional[str] = None,
         include_deactivated_user_workspaces: Optional[bool] = None,
         is_active: Optional[bool] = None,
         cursor: Optional[str] = None,