diff -r 48c1ee485dc0 -r 9b93fdd5ba30 src/pyams_content/workflow/notify.py
--- a/src/pyams_content/workflow/notify.py	Fri Nov 13 13:11:29 2020 +0100
+++ b/src/pyams_content/workflow/notify.py	Fri Nov 13 13:13:48 2020 +0100
@@ -74,9 +74,12 @@
                             else:
                                 restrictions = IManagerRestrictions(notification_source, None)
                                 if restrictions is not None:
-                                    principal_restrictions = restrictions.get_restrictions(principal)
-                                    if principal_restrictions.check_access(notification_source,
-                                                                           MANAGE_CONTENT_PERMISSION):
+                                    principal_restrictions = restrictions.get_restrictions(
+                                        principal)
+                                    if principal_restrictions and \
+                                            principal_restrictions.check_access(
+                                                notification_source,
+                                                MANAGE_CONTENT_PERMISSION):
                                         principals.add(principal)
                         else:
                             principals.add(principal)