diff --git a/psu.py b/psu.py
index 95c3ce0..6c2279b 100644
--- a/psu.py
+++ b/psu.py
@@ -12,10 +12,10 @@
 
 from transaction import commit, abort
 from zope.app.authentication.principalfolder import Principal
+from zope.app.catalog.interfaces import ICatalog
 from zope.app.component.hooks import setSite
 from zope.app.container.contained import ObjectAddedEvent, ObjectRemovedEvent
 from zope.cachedescriptors.property import Lazy
-from zope.catalog.interfaces import ICatalog
 from zope import component
 from zope.event import notify
 from zope.lifecycleevent import ObjectCreatedEvent, ObjectModifiedEvent