diff --git a/mitterlib/network/networkbase.py b/mitterlib/network/networkbase.py
index bf8abf6..6630a43 100644
--- a/mitterlib/network/networkbase.py
+++ b/mitterlib/network/networkbase.py
@@ -34,10 +34,15 @@ _log = logging.getLogger('mitterlib.network.Network')
 
 def auth_options(namespace, options, auths):
     """Convert the auth fields into options for the command line."""
+
+    default_values = {
+            'str': '',
+            'passwd': ''}
+
     for option in auths:
         options.add_option(group=namespace,
                 option=option['name'],
-                default=None,
+                default=default_values[option['type']],
                 help=option['help'],
                 *(option['flags']))
 #--------------------------------------------------------------------