diff --git a/lib/nova_plugins/hypervisor-libvirt b/lib/nova_plugins/hypervisor-libvirt
index 6f90f4a..42d3af1 100644
--- a/lib/nova_plugins/hypervisor-libvirt
+++ b/lib/nova_plugins/hypervisor-libvirt
@@ -108,6 +108,7 @@
     iniset $NOVA_CONF DEFAULT libvirt_type "$LIBVIRT_TYPE"
     iniset $NOVA_CONF DEFAULT libvirt_cpu_mode "none"
     iniset $NOVA_CONF DEFAULT use_usb_tablet "False"
+    iniset $NOVA_CONF DEFAULT default_ephemeral_format "ext4"
     iniset $NOVA_CONF DEFAULT compute_driver "libvirt.LibvirtDriver"
     LIBVIRT_FIREWALL_DRIVER=${LIBVIRT_FIREWALL_DRIVER:-"nova.virt.libvirt.firewall.IptablesFirewallDriver"}
     iniset $NOVA_CONF DEFAULT firewall_driver "$LIBVIRT_FIREWALL_DRIVER"