diff --git a/tests/app/service/test_rest.py b/tests/app/service/test_rest.py
index cd6bbae8f..316819da0 100644
--- a/tests/app/service/test_rest.py
+++ b/tests/app/service/test_rest.py
@@ -3376,8 +3376,8 @@ def test_get_monthly_notification_data_by_service(mocker, admin_request):
 
 def test_get_returned_letter_summary(admin_request, sample_service):
     create_returned_letter(sample_service, reported_at=datetime.utcnow())
-    create_returned_letter(sample_service, reported_at=datetime.utcnow()-timedelta(days=3))
+    create_returned_letter(sample_service, reported_at=datetime.utcnow() - timedelta(days=3))
 
     response = admin_request.get('service.returned_letter_summary', service_id=sample_service.id)
 
-    assert len(response) == 2
\ No newline at end of file
+    assert len(response) == 2