diff --git a/VERSION b/VERSION
index 1e71de9..ad0b729 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.3.29
+2.3.30
diff --git a/app/modules/invoice_error_finder/services/detection_service.py b/app/modules/invoice_error_finder/services/detection_service.py
index 3802ffa..cbd8fd6 100644
--- a/app/modules/invoice_error_finder/services/detection_service.py
+++ b/app/modules/invoice_error_finder/services/detection_service.py
@@ -628,10 +628,15 @@ class DetectionService:
 
     @staticmethod
     def _resolve_hub_customer_id(row: Dict[str, Any]) -> Optional[int]:
-        value = row.get("hub_customer_id") or row.get("customer_key")
-        if isinstance(value, int):
-            return value
-        return None
+        value = row.get("hub_customer_id")
+        if not isinstance(value, int):
+            return None
+
+        customer = execute_query_single(
+            "SELECT id FROM customers WHERE id = %s",
+            (value,),
+        )
+        return value if customer else None
 
     @staticmethod
     def _resolve_customer_name(hub_customer_id: Optional[int], fallback: Optional[str]) -> Optional[str]:
diff --git a/tests/test_invoice_error_finder.py b/tests/test_invoice_error_finder.py
index 0c82ee8..08490ab 100644
--- a/tests/test_invoice_error_finder.py
+++ b/tests/test_invoice_error_finder.py
@@ -179,6 +179,30 @@ def test_detection_service_reopens_expired_ignored_issue(monkeypatch):
     assert "ignored_until = NULL" in updates[0][0]
 
 
+def test_detection_service_ignores_non_hub_customer_keys(monkeypatch):
+    from app.modules.invoice_error_finder.services.detection_service import DetectionService
+
+    def fake_execute_query_single(query, params=None):
+        if "SELECT id FROM customers" in query:
+            return None
+        return None
+
+    monkeypatch.setattr(
+        "app.modules.invoice_error_finder.services.detection_service.execute_query_single",
+        fake_execute_query_single,
+    )
+
+    service = DetectionService()
+    customer_id = service._resolve_hub_customer_id(
+        {
+            "customer_key": 56283338,
+            "hub_customer_id": None,
+        }
+    )
+
+    assert customer_id is None
+
+
 def test_list_issues_supports_unassigned_filter(monkeypatch):
     from app.modules.invoice_error_finder.backend.router import list_issues