diff --git a/acme.sh b/acme.sh
index 7eee2909..d36df7f7 100755
--- a/acme.sh
+++ b/acme.sh
@@ -740,9 +740,9 @@ _hmac() {
 
   if [ "$alg" = "sha256" ] || [ "$alg" = "sha1" ]; then
     if [ "$outputhex" ]; then
-      $OPENSSL_BIN dgst -"$alg" -mac HMAC -macopt "hexkey:$secret_hex" | cut -d = -f 2 | tr -d ' '
+      ($OPENSSL_BIN dgst -"$alg" -mac HMAC -macopt "hexkey:$secret_hex" 2>/dev/null || $OPENSSL_BIN dgst -"$alg" -hmac "$(printf "%s" "$secret_hex" | _h2b)") | cut -d = -f 2 | tr -d ' '
     else
-      $OPENSSL_BIN dgst -"$alg" -mac HMAC -macopt "hexkey:$secret_hex" -binary
+      $OPENSSL_BIN dgst -"$alg" -mac HMAC -macopt "hexkey:$secret_hex" -binary 2>/dev/null || $OPENSSL_BIN dgst -"$alg" -hmac "$(printf "%s" "$secret_hex" | _h2b)" -binary
     fi
   else
     _err "$alg is not supported yet"