diff --git a/lib/classes/tools.js b/lib/classes/tools.js
index c8d8bd8..8e399cd 100644
--- a/lib/classes/tools.js
+++ b/lib/classes/tools.js
@@ -158,7 +158,7 @@ class tools extends emitter {
    */
   command(opts, block) {
     const flags = opts.flags.join(' ');
-    const proto = (opts.udp) ? ' -sU' : ' ';
+    const proto = (opts.udp) ? ' -sU' : '';
     const to = `--host-timeout=${opts.timeout}s `;
     const ipv6 = (validation.test(validation.patterns.IPv6, block)) ?
       ' -6 ' : ' ';