diff --git a/ckanext/harvest/model/__init__.py b/ckanext/harvest/model/__init__.py
index 8c4705f..a372de4 100644
--- a/ckanext/harvest/model/__init__.py
+++ b/ckanext/harvest/model/__init__.py
@@ -168,7 +168,7 @@ def define_harvester_tables():
     # Was harvested_document
     harvest_object_table = Table('harvest_object', metadata,
         Column('id', types.UnicodeText, primary_key=True, default=make_uuid),
-        Column('guid', types.UnicodeText, default=''),
+        Column('guid', types.UnicodeText, default=u''),
         Column('current',types.Boolean,default=False),
         Column('gathered', types.DateTime, default=datetime.datetime.utcnow),
         Column('fetch_started', types.DateTime),