--- a/src/mailman/model/mailinglist.py	2014-04-23 14:29:53.000000000 +0200
+++ b/src/mailman/model/mailinglist.py	2014-06-21 21:36:08.058811806 +0200
@@ -585,6 +585,7 @@ class ListArchiverSet:
         # with the mailing list.
         store = Store.of(self._mailing_list)
         for archiver_name in system_archivers:
+            archiver_name = unicode(archiver_name)
             exists = store.find(
                 ListArchiver,
                 And(ListArchiver.mailing_list == mailing_list,