diff --git a/backend/src/cyclone/reconcile.py b/backend/src/cyclone/reconcile.py
index e175eca..1989a29 100644
--- a/backend/src/cyclone/reconcile.py
+++ b/backend/src/cyclone/reconcile.py
@@ -27,7 +27,7 @@ WINDOW_DAYS_DEFAULT = 7
 
 class _ClaimLike(Protocol):
     id: str
-    patient_control_number: str
+    patient_control_number: Optional[str]  # truthy-filtered in match()
     service_date_from: Optional[date]
     matched_remittance_id: Optional[str]