diff --git a/tests/factories.py b/tests/factories.py
index 8b78ffc5..efb6fb82 100644
--- a/tests/factories.py
+++ b/tests/factories.py
@@ -289,6 +289,7 @@ class TaskOrderFactory(Base):
     )
     number = factory.LazyFunction(random_task_order_number)
     creator = factory.SubFactory(UserFactory)
+    signed_at = None
     _pdf = factory.SubFactory(AttachmentFactory)
 
     @classmethod