--- a/cubicweb/server/hook.py	Sat Feb 01 22:01:00 2020 +0100
+++ b/cubicweb/server/hook.py	Tue Feb 11 10:20:18 2020 +0100
@@ -522,8 +522,8 @@
     """
     __select__ = enabled_category()
     # set this in derivated classes
+    category = None
     events: Union[None, Tuple[str], Tuple[str, str]] = None
-    category: Union[None, str] = None
     order = 0
     # stop pylint from complaining about missing attributes in Hooks classes
     eidfrom = eidto = entity = rtype = repo = None