diff --git a/backend/app/main.py b/backend/app/main.py
index e27b1fc..4531a75 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -15,6 +15,7 @@ from app.core.database import Base, SessionLocal, engine
 from app.core.security import add_api_key, generate_api_key, require_admin_auth
 from app.middleware.security import SecurityHeadersMiddleware
 from app.models.mail_source import MailSource  # noqa: F401 – ensure table is registered
+from app.models.user import User  # noqa: F401 – ensure mapper is registered before UserDomain resolves "User"
 from app.services.imap_client import IMAPClient
 from app.services.report_store import ReportStore