Index: /trunk/packages/sipb-xen-www/code/validation.py
===================================================================
--- /trunk/packages/sipb-xen-www/code/validation.py	(revision 536)
+++ /trunk/packages/sipb-xen-www/code/validation.py	(revision 537)
@@ -60,5 +60,5 @@
         machine_id = None
     disk_usage = Disk.query().filter_by(Disk.c.machine_id != machine_id,
-                                        owner=user).sum(Disk.c.size)
+                                        owner=user).sum(Disk.c.size) or 0
     return min(MAX_DISK_SINGLE, MAX_DISK_TOTAL-disk_usage/1024.)