diff --git a/xo-install.sh b/xo-install.sh
index 7070d46..c11500f 100755
--- a/xo-install.sh
+++ b/xo-install.sh
@@ -42,6 +42,7 @@ PATH_TO_HTTPS_KEY="${PATH_TO_HTTPS_KEY:-""}"
 PATH_TO_HOST_CA="${PATH_TO_HOST_CA:-""}"
 AUTOCERT="${AUTOCERT:-"false"}"
 ACME="${ACME:-"false"}"
+ACME_EMAIL="${ACME_EMAIL:-""}"
 ACME_CA="${ACME_CA:-"letsencrypt/production"}"
 USESUDO="${USESUDO:-"false"}"
 GENSUDO="${GENSUDO:-"false"}"