diff --git a/tools/python/xen/xend/server/DevController.py b/tools/python/xen/xend/server/DevController.py
index 83363f9281..eed63ebbf9 100644
--- a/tools/python/xen/xend/server/DevController.py
+++ b/tools/python/xen/xend/server/DevController.py
@@ -57,6 +57,8 @@ class DevController:
         @return The ID for the newly created device.
         """
         (devid, back, front) = self.getDeviceDetails(config)
+        if devid is None:
+            return 0
 
         self.writeDetails(config, devid, back, front)
 
diff --git a/tools/python/xen/xend/server/blkif.py b/tools/python/xen/xend/server/blkif.py
index d60607f0f4..b3b1247e6c 100644
--- a/tools/python/xen/xend/server/blkif.py
+++ b/tools/python/xen/xend/server/blkif.py
@@ -43,7 +43,7 @@ class BlkifController(DevController):
         
         dev = sxp.child_value(config, 'dev')
         if re.match('^ioemu:', dev):
-            return (0,{},{})
+            return (None,{},{})
 
         devid = blkif.blkdev_name_to_number(dev)