diff --git a/nova/block_device.py b/nova/block_device.py
index caa521e83..aec981933 100644
--- a/nova/block_device.py
+++ b/nova/block_device.py
@@ -71,7 +71,7 @@ _dev = re.compile('^/dev/')
 
 def strip_dev(device_name):
     """remove leading '/dev/'"""
-    return _dev.sub('', device_name)
+    return _dev.sub('', device_name) if device_name else device_name
 
 
 _pref = re.compile('^((x?v|s)d)')