On the face of it, it looks like the following patch should fix it: https://github.com/libguestfs/nbdkit/commit/a6b907e5359a139404cee5fd5c7f94eab36a5fde
What I don't understand is why that isn't included in your nbdkit (1.1.25) already? In any case the latest nbdkit -- 1.1.27 released a couple of days ago -- does pass all the tests with the latest qemu. The valgrind tests are broken with 1.1.27, and that is fixed by the following 3 commits added after 1.1.27: https://github.com/libguestfs/nbdkit/commit/1e51756907646bc8d2dbcddb2cdb9cea59e5c7bf https://github.com/libguestfs/nbdkit/commit/a3d4a17971bbd84639437a52f5ab1b3fd307c29d https://github.com/libguestfs/nbdkit/commit/b67a2099105a949b9e943b8c8fc8da1c0163c641 Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/