diff --git a/saferm.sh b/saferm.sh
index aa96c29..2e44e54 100644
--- a/saferm.sh
+++ b/saferm.sh
@@ -14,6 +14,8 @@ function failexit () {
   exit $1
 }
 
+set -u # disallow unset vars 
+
 # xxxxx TODO CHANGEME
 dest=/mnt/tmp