--- xen-3.0.3-testing-11633/./tools/python/build/lib.linux-x86_64-2.4/xen/xend/server/blkif.py.orig	2006-09-28 18:52:39.000000000 -0400
+++ xen-3.0.3-testing-11633/./tools/python/build/lib.linux-x86_64-2.4/xen/xend/server/blkif.py	2006-10-18 15:58:28.000000000 -0400
@@ -81,6 +81,9 @@ class BlkifController(DevController):
                          'acm_policy' : policy})
 
         devid = blkif.blkdev_name_to_number(dev)
+        if not devid:
+            raise VmError('Unable to find number for device (%s)'%(dev))
+
         front = { 'virtual-device' : "%i" % devid,
                   'device-type' : dev_type
                 }