diff --git a/lib/neutron b/lib/neutron
index b857e31..9f9b132 100644
--- a/lib/neutron
+++ b/lib/neutron
@@ -325,9 +325,10 @@
 }
 
 # Make Neutron-required changes to nova.conf
-# Takes a single argument which is the config file to update.
+# Takes a single optional argument which is the config file to update,
+# if not passed $NOVA_CONF is used.
 function configure_neutron_nova_new {
-    local conf="$1"
+    local conf=${1:-$NOVA_CONF}
     iniset $conf DEFAULT use_neutron True
     iniset $conf neutron auth_type "password"
     iniset $conf neutron auth_url "$KEYSTONE_SERVICE_URI"
diff --git a/lib/neutron-legacy b/lib/neutron-legacy
index 2e8992d..bee032a 100644
--- a/lib/neutron-legacy
+++ b/lib/neutron-legacy
@@ -366,7 +366,7 @@
 }
 
 function create_nova_conf_neutron {
-    local conf="$1"
+    local conf=${1:-$NOVA_CONF}
     iniset $conf DEFAULT use_neutron True
     iniset $conf neutron auth_type "password"
     iniset $conf neutron auth_url "$KEYSTONE_AUTH_URI"