diff --git a/python/mocha-shell.py b/python/mocha-shell.py
index 1615846..1f705ec 100644
--- a/python/mocha-shell.py
+++ b/python/mocha-shell.py
@@ -191,8 +191,6 @@ class MochaShell (REPLApplication):
 		return prompt
 
 	def process_input(self, value):
-		print(value)
-
 		parms = value.split(' ')
 
 		if len(parms) > 0:
@@ -367,9 +365,13 @@ class MochaShell (REPLApplication):
 					ik_User = self.oms.get_instance_by_global_identifier(KnownClassGuids.User)
 					ik_UserName = self.oms.get_instance_by_global_identifier(KnownAttributeGuids.UserName)
 
+					users = self.oms.get_instances(ik_User)
+					if users is None:
+						self.print_error_not_open()
+						return
+
 					print ("user name            ")
 					print ("---------------------")
-					users = self.oms.get_instances(ik_User)
 					for user in users:
 						user_name = self.oms.get_attribute_value(user, ik_UserName)
 						print(user_name)
diff --git a/python/mocha/oms/Oms.py b/python/mocha/oms/Oms.py
index 92bf07d..c6fc348 100644
--- a/python/mocha/oms/Oms.py
+++ b/python/mocha/oms/Oms.py
@@ -8,6 +8,7 @@ class Oms:
 		pass
 
 	def get_user_by_username(self, username : str):
+		
 		ik_User = self.get_instance_by_global_identifier(KnownClassGuids.User)
 		if ik_User is None:
 			print ("error: class `User` is not defined")
diff --git a/python/mocha/oms/db/sqlite/SQLiteDatabaseOms.py b/python/mocha/oms/db/sqlite/SQLiteDatabaseOms.py
index 33dfd3d..e36dd25 100644
--- a/python/mocha/oms/db/sqlite/SQLiteDatabaseOms.py
+++ b/python/mocha/oms/db/sqlite/SQLiteDatabaseOms.py
@@ -214,6 +214,9 @@ class SQLiteDatabaseOms (DatabaseOms):
 
 
 	def get_instances(self, of_class : InstanceReference = None):
+
+		if self.conn is None:
+			return None
 		
 		if of_class is not None:
 
@@ -244,6 +247,9 @@ class SQLiteDatabaseOms (DatabaseOms):
 		return InstanceReference(int(result[0]), InstanceKey(int(result[1]), int(result[2])), Guid.parse(result[3]))
 
 	def get_instance_by_global_identifier(self, global_identifier : Guid):
+		if self.conn is None:
+			return None
+
 		cursor = self.conn.execute("SELECT * FROM instances WHERE global_identifier = ?", [ global_identifier.strip() ])
 		results = cursor.fetchall()
 		if len(results) > 0: