diff --git a/templates/disclaimer.sh.j2 b/templates/disclaimer.sh.j2
index 1434cea..93348c4 100644
--- a/templates/disclaimer.sh.j2
+++ b/templates/disclaimer.sh.j2
@@ -1,4 +1,5 @@
 #!/bin/bash
+set -euo pipefail
 # Clean up when done or when aborting.
 trap "rm -f in.$$" 0 1 2 3 15
 
diff --git a/templates/letsencrypt_update.sh.j2 b/templates/letsencrypt_update.sh.j2
index 8d39365..c12cdae 100644
--- a/templates/letsencrypt_update.sh.j2
+++ b/templates/letsencrypt_update.sh.j2
@@ -1,4 +1,5 @@
 #/bin/bash
+set -euo pipefail
 FQDN='{{ mail_server_fqdn }}'
 cat "/etc/letsencrypt/live/${FQDN}/privkey.pem" "/etc/letsencrypt/live/${FQDN}/fullchain.pem" > /etc/courier/${FQDN}.imapd.pem
 chmod 600 "/etc/courier/${FQDN}.imapd.pem"