diff --git a/lib/cluster.js b/lib/cluster.js
index e05de4568bc..4e9e3e29d3e 100644
--- a/lib/cluster.js
+++ b/lib/cluster.js
@@ -307,17 +307,19 @@ function masterInit() {
     workerEnv = util._extend(workerEnv, env);
     workerEnv.NODE_UNIQUE_ID = '' + id;
 
-    for (var i = 0; i < execArgv.length; i++) {
-      var match = execArgv[i].match(/^(--debug|--debug-brk)(=\d+)?$/);
+    if (1024 < debugPort < 65535) {
+      for (var i = 0; i < execArgv.length; i++) {
+        var match = execArgv[i].match(/^(--debug|--debug-brk)(=\d+)?$/);
 
-      if (match) {
-        execArgv[i] = match[1] + '=' + debugPort;
-        hasDebugArg = true;
+        if (match) {
+          execArgv[i] = match[1] + '=' + debugPort;
+          hasDebugArg = true;
+        }
       }
-    }
 
     if (!hasDebugArg)
       execArgv = ['--debug-port=' + debugPort].concat(execArgv);
+    }
 
     return fork(cluster.settings.exec, cluster.settings.args, {
       env: workerEnv,