diff --git a/lib/smtp-connection.js b/lib/smtp-connection.js
index 66004e2..283cfba 100644
--- a/lib/smtp-connection.js
+++ b/lib/smtp-connection.js
@@ -1107,7 +1107,7 @@ class SMTPConnection extends EventEmitter {
                     this.remotePort = value;
                     break;
                 case 'HELO':
-                    value = Number(value) || 0;
+                    value = (value || '').toString().toLowerCase();
                     this._server.logger.info(
                         {
                             tnx: 'xforward',