diff --git a/scripts/backup b/scripts/backup
index 42c7b13..bf077e9 100644
--- a/scripts/backup
+++ b/scripts/backup
@@ -2,7 +2,7 @@
 #!/bin/bash
 
 # causes the shell to exit if any subcommand or pipeline returns a non-zero status
-set -e
+set -eu
 
 # Source YNH helpers
 . /usr/share/yunohost/helpers