diff --git a/devstack-vm-gate.sh b/devstack-vm-gate.sh
index 9ff5fb29..381acb2f 100755
--- a/devstack-vm-gate.sh
+++ b/devstack-vm-gate.sh
@@ -59,6 +59,7 @@ function setup_localrc {
     if [[ "$DEVSTACK_GATE_CEPH" == "1" ]]; then
         echo "CINDER_ENABLED_BACKENDS=ceph:ceph" >>localrc
         echo "TEMPEST_STORAGE_PROTOCOL=ceph" >>localrc
+        echo "CEPH_LOOPBACK_DISK_SIZE=8G" >>localrc
     fi
 
     # the exercises we *don't* want to test on for devstack