diff --git a/packages/mcp-fastmcp/src/keycardai/mcp/integrations/fastmcp/middleware.py b/packages/mcp-fastmcp/src/keycardai/mcp/integrations/fastmcp/middleware.py
index 55e0f3a2..67e63f1c 100644
--- a/packages/mcp-fastmcp/src/keycardai/mcp/integrations/fastmcp/middleware.py
+++ b/packages/mcp-fastmcp/src/keycardai/mcp/integrations/fastmcp/middleware.py
@@ -85,6 +85,9 @@ def __init__(
             zone_url: OAuth server zone URL (from environment if not provided)
             client_name: OAuth client name for registration
         """
+        if zone_url is None and client is not None:
+            zone_url = client.base_url
+
         settings = AccessMiddlewareSettings.model_validate({
             "zone_url": zone_url,
             "client_name": client_name,