diff --git a/lib/cluster.js b/lib/cluster.js
index 9f70c0273c..cbccd02605 100644
--- a/lib/cluster.js
+++ b/lib/cluster.js
@@ -278,11 +278,11 @@ function masterInit() {
     cluster.emit('setup', settings);
   }
 
+  var debugPortOffset = 1;
+
   function createWorkerProcess(id, env) {
     var workerEnv = util._extend({}, process.env);
     var execArgv = cluster.settings.execArgv.slice();
-    var debugPort = process.debugPort + id;
-    var hasDebugArg = false;
 
     workerEnv = util._extend(workerEnv, env);
     workerEnv.NODE_UNIQUE_ID = '' + id;
@@ -291,14 +291,12 @@ function masterInit() {
       var match = execArgv[i].match(/^(--debug|--debug-(brk|port))(=\d+)?$/);
 
       if (match) {
+        let debugPort = process.debugPort + debugPortOffset;
+        ++debugPortOffset;
         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,
       silent: cluster.settings.silent,
diff --git a/test/parallel/test-cluster-debug-port.js b/test/parallel/test-cluster-debug-port.js
new file mode 100644
index 0000000000..1a42850e9b
--- /dev/null
+++ b/test/parallel/test-cluster-debug-port.js
@@ -0,0 +1,38 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cluster = require('cluster');
+
+if (cluster.isMaster) {
+  assert.strictEqual(process.execArgv.length, 0, 'run test with no args');
+
+  function checkExitCode(code, signal) {
+    assert.strictEqual(code, 0);
+    assert.strictEqual(signal, null);
+  }
+
+  console.log('forked worker should not have --debug-port');
+  cluster.fork().on('exit', checkExitCode);
+
+  cluster.setupMaster({
+    execArgv: ['--debug-port=' + process.debugPort]
+  });
+
+  console.log('forked worker should have --debug-port, with offset = 1');
+  cluster.fork({
+    portSet: process.debugPort + 1
+  }).on('exit', checkExitCode);
+
+  console.log('forked worker should have --debug-port, with offset = 2');
+  cluster.fork({
+    portSet: process.debugPort + 2
+  }).on('exit', checkExitCode);
+} else {
+  const hasDebugArg = process.execArgv.some(function(arg) {
+    return /debug/.test(arg);
+  });
+
+  assert.strictEqual(hasDebugArg, process.env.portSet !== undefined);
+  assert.strictEqual(process.debugPort, +process.env.portSet || 5858);
+  process.exit();
+}