diff --git a/controller/Database.py b/controller/Database.py
index 8262d3a..f360b6c 100644
--- a/controller/Database.py
+++ b/controller/Database.py
@@ -20,9 +20,6 @@ class Database( object ):
   ID_BITS = 128 # number of bits within an id
   ID_DIGITS = "0123456789abcdefghijklmnopqrstuvwxyz"
 
-  POSTGRESQL_BACKEND = 0
-  SQLITE_BACKEND = 1
-
   # caching Notebooks causes problems because different users have different read_write/owner values
   CLASSES_NOT_TO_CACHE = ( Notebook, )
 
@@ -71,7 +68,7 @@ class Database( object ):
       self.__connection = connection or \
         Connection_wrapper( sqlite.connect( "luminotes.db", detect_types = sqlite.PARSE_DECLTYPES, check_same_thread = False ) )
       self.__pool = None
-      self.__backend = Database.SQLITE_BACKEND
+      self.__backend = Persistent.SQLITE_BACKEND
     else:
       import psycopg2 as psycopg
       from psycopg2.pool import PersistentConnectionPool
@@ -100,7 +97,7 @@ class Database( object ):
           ),
         )
 
-      self.__backend = Database.POSTGRESQL_BACKEND
+      self.__backend = Persistent.POSTGRESQL_BACKEND
 
     self.__cache = cache