diff --git a/src/_zkapauthorizer/controller.py b/src/_zkapauthorizer/controller.py
index 3181685fd4688fe45872c1c706dd6460aecf346e..edda44e5b90b03bccdc08d7667e2300824a85956 100644
--- a/src/_zkapauthorizer/controller.py
+++ b/src/_zkapauthorizer/controller.py
@@ -85,6 +85,7 @@ class UnrecognizedFailureReason(Exception):
 
     The redemption attempt may be automatically retried at some point.
     """
+
     response = attr.ib()