diff --git a/devstack-vm-gate-host.sh b/devstack-vm-gate-host.sh
index 2401fff6..51735851 100755
--- a/devstack-vm-gate-host.sh
+++ b/devstack-vm-gate-host.sh
@@ -86,6 +86,10 @@ if [ "$DEVSTACK_GATE_TEMPEST" -eq "1" ]; then
     # We need to disable ratelimiting when running
     # Tempest tests since so many requests are executed
     echo "API_RATE_LIMIT=False" >> localrc
+    # Volume tests in Tempest require a number of volumes
+    # to be created, each of 1G size. Devstack's default
+    # volume backing file size is 2G, so we increase to 4G
+    echo "VOLUME_BACKING_FILE_SIZE=4G" >> localrc
 fi
 
 # The vm template update job should cache some images in ~/files.