diff --git a/same-server-authenticator-hook.sh b/same-server-authenticator-hook.sh
index 67b3e0d..3b49d7b 100755
--- a/same-server-authenticator-hook.sh
+++ b/same-server-authenticator-hook.sh
@@ -2,7 +2,7 @@
 set -x
 DOMAIN=$(expr match "$CERTBOT_DOMAIN" '.*\.\(.*\..*\)')
 CHALLENGE_DOMAIN="_acme-challenge.${CERTBOT_DOMAIN}"
-
+[[ -z ${DOMAIN} ]] && export DOMAIN=${CERTBOT_DOMAIN}
 knotc zone-begin ${DOMAIN}
 knotc zone-set ${DOMAIN} _acme-challenge.${CERTBOT_DOMAIN}. 360 TXT ${CERTBOT_VALIDATION}
 knotc zone-commit ${DOMAIN}
diff --git a/same-server-cleanup.sh b/same-server-cleanup.sh
index e487719..6c44901 100755
--- a/same-server-cleanup.sh
+++ b/same-server-cleanup.sh
@@ -2,7 +2,7 @@
 
 DOMAIN=$(expr match "$CERTBOT_DOMAIN" '.*\.\(.*\..*\)')
 CHALLENGE_DOMAIN="_acme-challenge.${CERTBOT_DOMAIN}"
-
+[[ -z ${DOMAIN} ]] && export DOMAIN=${CERTBOT_DOMAIN}
 knotc zone-begin ${DOMAIN}
 knotc zone-unset ${DOMAIN} _acme-challenge.${CERTBOT_DOMAIN}. TXT
 knotc zone-commit ${DOMAIN}