diff --git a/chassis/db_context.py b/chassis/db_context.py
index 5ca122a..06569bc 100644
--- a/chassis/db_context.py
+++ b/chassis/db_context.py
@@ -7,7 +7,7 @@ from chassis.consts import const
 engines = {}
 
 
-def init_engine(config_item):
+def init_engine(config_item=None):
     if config_item:
         databases = config_item[const.DB_CONFIG_ITEM]
     else: