diff --git a/srcloner.py b/srcloner.py
index c49d15a..18106b9 100644
--- a/srcloner.py
+++ b/srcloner.py
@@ -343,10 +343,10 @@ def main():
     parser.add_argument('--srid', dest='srid', required=True)
     for ops in stoneridge.OPERATING_SYSTEMS:
         parser.add_argument('--%s' % (ops,), dest='operating_systems',
-                action='append_const', const=ops)
+                action='append_const', const=ops, default=[])
     for nc in stoneridge.NETCONFIGS:
         parser.add_argument('--%s' % (nc,), dest='netconfigs',
-                action='append_const', const=nc)
+                action='append_const', const=nc, default=[])
     parser.add_argument('--attempt', dest='attempt', required=True, type=int)
     parser.add_argument('--ldap', dest='ldap', default='')
     parser.add_argument('--sha', dest='sha', default='')
diff --git a/srdeferrer.py b/srdeferrer.py
index ec73c42..f31794b 100644
--- a/srdeferrer.py
+++ b/srdeferrer.py
@@ -55,10 +55,10 @@ def main():
     parser.add_argument('--sha', dest='sha', default='')
     for nc in stoneridge.NETCONFIGS:
         parser.add_argument('--%s' % (nc,), dest='netconfigs',
-                action='append_const', const=nc)
+                action='append_const', const=nc, default=[])
     for ops in stoneridge.OPERATING_SYSTEMS:
         parser.add_argument('--%s' % (nc,), dest='operating_systems',
-                action='append_const', const=ops)
+                action='append_const', const=ops, default=[])
 
     args = parser.parse_args()