Storage Pool - NFS v4.1

Hello, In order to use pNFS which is only available in NFS version 4.1, I'm trying to create a netfs storage pool specifying the protocol version to be used : <pool type="netfs"> <name>vms</name> <source> ... <format type="nfs"/> <protocol ver='4.1'/> </source> <target> ... </pool> But the storage pool XML documentation [1] states that : protocol For a netfs Storage Pool provide a mechanism to define which NFS protocol version number will be used to contact the server's NFS service. The attribute ver accepts an unsigned *integer* as the version number to use. And indeed, when I try to virsh pool-define I get : error: Failed to define pool from pool.xml error: XML error: storage pool protocol ver '4.1' is malformed How can I specify the desired NFS minor version to libvirt ? I could mount the NFS share myself and build a dir storage pool on top of it but that's not very pretty. Thank you, [1] https://libvirt.org/formatstorage.html -- Charles