diff --git a/scrapy/downloadermiddlewares/retry.py b/scrapy/downloadermiddlewares/retry.py
index 5963dacdf..b8ead12ce 100644
--- a/scrapy/downloadermiddlewares/retry.py
+++ b/scrapy/downloadermiddlewares/retry.py
@@ -34,8 +34,8 @@ logger = logging.getLogger(__name__)
 def get_retry_request(
     request,
     *,
-    reason,
     spider,
+    reason='unspecified',
     max_retry_times=None,
     priority_adjust=None,
 ):