--- xen-4.1.0/tools/libxl/libxl.c.orig	2011-01-25 19:22:58.000000000 +0000
+++ xen-4.1.0/tools/libxl/libxl.c	2011-01-27 20:23:57.000000000 +0000
@@ -988,13 +988,18 @@
         case PHYSTYPE_VHD:
             if (libxl__blktap_enabled(&gc))
                 dev = libxl__blktap_devpath(&gc, disk->physpath, phystype);
+            else
+                dev = disk->physpath;
             break;
 
         default:
             LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "unrecognized disk physical type: %d\n", phystype);
             break;
     }
-    ret = strdup(dev);
+    if (dev)
+        ret = strdup(dev);
+    else
+        ret = NULL;
     libxl__free_all(&gc);
     return ret;
 }