diff --git a/offlineimap/CustomConfig.py b/offlineimap/CustomConfig.py
index b528e70..7dce4a6 100644
--- a/offlineimap/CustomConfig.py
+++ b/offlineimap/CustomConfig.py
@@ -165,7 +165,7 @@ def CustomConfigDefault():
 
 
 
-class ConfigHelperMixin:
+class ConfigHelperMixin(object):
     """Allow comfortable retrieving of config values pertaining
     to a section.