diff --git a/dehydrated b/dehydrated
index 5c6af3f..ba6fdf4 100755
--- a/dehydrated
+++ b/dehydrated
@@ -717,7 +717,7 @@ command_sign_domains() {
   # Generate certificates for all domains found in domains.txt. Check if existing certificate are about to expire
   ORIGIFS="${IFS}"
   IFS=$'\n'
-  for line in $(<"${DOMAINS_TXT}" tr -d '\r' | tr '[:upper:]' '[:lower:]' | _sed -e 's/^[[:space:]]*//g' -e 's/[[:space:]]*$//g' -e 's/[[:space:]]+/ /g' | (grep -vE '^(#|$)' || true)); do
+  for line in $(<"${DOMAINS_TXT}" tr -d '\r' | awk '{print tolower($0)}' | _sed -e 's/^[[:space:]]*//g' -e 's/[[:space:]]*$//g' -e 's/[[:space:]]+/ /g' | (grep -vE '^(#|$)' || true)); do
     reset_configvars
     IFS="${ORIGIFS}"
     domain="$(printf '%s\n' "${line}" | cut -d' ' -f1)"