diff --git a/swh/model/hypothesis_strategies.py b/swh/model/hypothesis_strategies.py
index 19a8d89118f1e6b522b2f8af61ff6a1337515e38..45671861f8c8a6f1215bc1fc758505d9b7722845 100644
--- a/swh/model/hypothesis_strategies.py
+++ b/swh/model/hypothesis_strategies.py
@@ -56,7 +56,8 @@ from .model import (
 from .swhids import ExtendedObjectType, ExtendedSWHID
 
 pgsql_alphabet = characters(
-    blacklist_categories=("Cs",), blacklist_characters=["\u0000"]
+    blacklist_categories=["Cs"],
+    blacklist_characters=["\u0000"],
 )  # postgresql does not like these