diff --git a/acme.sh b/acme.sh
index 8d422719..b408ed30 100755
--- a/acme.sh
+++ b/acme.sh
@@ -2357,7 +2357,7 @@ _startserver() {
 echo 'HTTP/1.0 200 OK'; \
 echo 'Content-Length\: $_content_len'; \
 echo ''; \
-printf -- '$content';" &
+printf '%s' '$content';" &
   serverproc="$!"
 }