diff --git a/elements/ubuntu/root.d/10-cache-ubuntu-tarball b/elements/ubuntu/root.d/10-cache-ubuntu-tarball
index ebef6470..757fea15 100755
--- a/elements/ubuntu/root.d/10-cache-ubuntu-tarball
+++ b/elements/ubuntu/root.d/10-cache-ubuntu-tarball
@@ -1,7 +1,7 @@
 #!/bin/bash
 # These are useful, or at worst not harmful, for all images we build.
 
-set -eu
+set -eux
 set -o pipefail
 
 [ -n "$ARCH" ]