--- a/wokkel/mam.py	Thu Apr 23 13:35:21 2015 +0200
+++ b/wokkel/mam.py	Thu Apr 23 14:19:43 2015 +0200
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 # -*- test-case-name: wokkel.test.test_mam -*-
 #
 # SàT Wokkel extension for Message Archive Management (XEP-0313)
@@ -157,8 +158,9 @@
     @type never: C{list}
     """
 
-    def __init__(self, default, always=None, never=None):
-        assert default in ('always', 'never', 'roster')
+    def __init__(self, default=None, always=None, never=None):
+        if default is not None:
+            assert default in ('always', 'never', 'roster')
         self.default = default
         if always is not None:
             assert isinstance(always, list)