diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 8d96858..064464b 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -246,6 +246,8 @@
 # Unless you have a custom Keystone service catalog implementation, you
 # probably want to leave this value as "volume"
 catalog_type = volume
+# The disk format to use when copying a volume to image
+disk_format = raw
 # Number of seconds to wait while looping to check the status of a
 # volume that is being made available
 build_interval = 10