diff --git a/backend/magic_plan/tests/test_magic_plan_service.py b/backend/magic_plan/tests/test_magic_plan_service.py
index 65c19b7a..70099e91 100644
--- a/backend/magic_plan/tests/test_magic_plan_service.py
+++ b/backend/magic_plan/tests/test_magic_plan_service.py
@@ -198,3 +198,31 @@ def test_run_uploads_to_s3_with_uprn_key(
         S3_BUCKET,
         f"documents/uprn/100023336956/magic_plan_{plan_summary.id}.json.gz",
     )
+
+
+def test_run_uploads_to_s3_with_deal_id_key_when_uprn_absent(
+    mock_client: MagicMock,
+    api_magic_plan: MagicPlanPlan,
+    plan_summary: PlanSummary,
+) -> None:
+    # Arrange
+    mock_client.get_plans.return_value.plans = [plan_summary]
+    mock_client.get_plan.return_value = api_magic_plan
+    request = _make_request(hubspot_deal_id="deal-456", uprn=None)
+    service = MagicPlanService(client=mock_client, s3_bucket=S3_BUCKET)
+    with patch(
+        "backend.magic_plan.magic_plan_service.find_matching_plan",
+        return_value=plan_summary,
+    ), patch("backend.magic_plan.magic_plan_service.save_plan"), patch(
+        "backend.magic_plan.magic_plan_service.db_session"
+    ), patch(
+        "backend.magic_plan.magic_plan_service.save_data_to_s3"
+    ) as mock_s3:
+        # Act
+        service.run(request)
+    # Assert
+    mock_s3.assert_called_once_with(
+        ANY,
+        S3_BUCKET,
+        f"documents/hubspot_deal_id/deal-456/magic_plan_{plan_summary.id}.json.gz",
+    )