diff --git a/evomaintenance.sh b/evomaintenance.sh
index 97a8dff..f5437d9 100644
--- a/evomaintenance.sh
+++ b/evomaintenance.sh
@@ -7,9 +7,6 @@
 # version 0.3
 # Copyright 2007-2018 Gregory Colpart <reg@evolix.fr>, Jérémy Lecour <jlecour@evolix.fr>, Evolix <info@evolix.fr>
 
-# Treat unset variables as an error when substituting.
-set -u
-
 test -f /etc/evomaintenance.cf && . /etc/evomaintenance.cf
 
 [ -n "${HOSTNAME}" ]          || HOSTNAME=$(hostname)
@@ -17,6 +14,10 @@ test -f /etc/evomaintenance.cf && . /etc/evomaintenance.cf
 [ -n "${EVOMAINTMAIL}" ]      || EVOMAINTMAIL=evomaintenance-$(echo "${HOSTNAME_INTERNAL}" | cut -d- -f1)@${REALM}
 [ -n "${LOGFILE}" ]           || LOGFILE=/var/log/evomaintenance.log
 
+# Treat unset variables as an error when substituting.
+# Only after this line, because some config variables might be missing.
+set -u
+
 if [ "${HOSTNAME}" = "${HOSTNAME_INTERNAL}" ]; then
     HOSTNAME_TEXT="${HOSTNAME}"
 else