--- a/cubicweb/server/hook.py	Tue Feb 11 10:20:18 2020 +0100
+++ b/cubicweb/server/hook.py	Tue Feb 11 10:22:52 2020 +0100
@@ -248,7 +248,6 @@
 
 from logging import getLogger
 from itertools import chain
-from typing import Union, Tuple
 
 from logilab.common.decorators import classproperty, cached
 from logilab.common.logging_ext import set_log_methods
@@ -522,8 +521,8 @@
     """
     __select__ = enabled_category()
     # set this in derivated classes
+    events = None
     category = None
-    events: Union[None, Tuple[str], Tuple[str, str]] = None
     order = 0
     # stop pylint from complaining about missing attributes in Hooks classes
     eidfrom = eidto = entity = rtype = repo = None