Index: src/FluentNHibernate/Cfg/Db/PersistenceConfiguration.cs
===================================================================
--- src/FluentNHibernate/Cfg/Db/PersistenceConfiguration.cs	(revision 442)
+++ src/FluentNHibernate/Cfg/Db/PersistenceConfiguration.cs	(working copy)
@@ -29,6 +29,7 @@
         protected const string DriverClassKey = "connection.driver_class";
         protected const string ConnectionStringKey = "connection.connection_string";
         protected const string ProxyFactoryFactoryClassKey = "proxyfactory.factory_class";
+        protected const string DefaultProxyFactoryFactoryClassName = "NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle";
         protected const string AdoNetBatchSizeKey = "adonet.batch_size";
 
         private readonly Dictionary<string, string> _rawValues;
@@ -44,6 +45,7 @@
             _rawValues = new Dictionary<string, string>();
             _values = new Cache<string, string>(_rawValues, s=>"");
             _values.Store(ConnectionProviderKey, DefaultConnectionProviderClassName);
+            _values.Store(ProxyFactoryFactoryClassKey, DefaultProxyFactoryFactoryClassName);
             connectionString = new TConnectionString();
         }