diff --git a/lib/cluster.js b/lib/cluster.js
index 22d213ba227e2a..77726079602a64 100644
--- a/lib/cluster.js
+++ b/lib/cluster.js
@@ -299,6 +299,7 @@ function masterInit() {
   function createWorkerProcess(id, env) {
     var workerEnv = util._extend({}, process.env);
     var execArgv = cluster.settings.execArgv.slice();
+    var debugPort = 0;
 
     workerEnv = util._extend(workerEnv, env);
     workerEnv.NODE_UNIQUE_ID = '' + id;
@@ -307,8 +308,11 @@ function masterInit() {
       var match = execArgv[i].match(/^(--debug|--debug-(brk|port))(=\d+)?$/);
 
       if (match) {
-        const debugPort = process.debugPort + debugPortOffset;
-        ++debugPortOffset;
+        if (debugPort === 0) {
+          debugPort = process.debugPort + debugPortOffset;
+          ++debugPortOffset;
+        }
+
         execArgv[i] = match[1] + '=' + debugPort;
       }
     }
diff --git a/test/parallel/test-cluster-debug-port.js b/test/parallel/test-cluster-debug-port.js
index e8f3f58b9534db..70203124ef0f66 100644
--- a/test/parallel/test-cluster-debug-port.js
+++ b/test/parallel/test-cluster-debug-port.js
@@ -22,6 +22,11 @@ if (cluster.isMaster) {
     portSet: process.debugPort + 1
   }).on('exit', checkExitCode);
 
+  cluster.setupMaster({
+    execArgv: [`--debug-port=${process.debugPort}`,
+               `--debug=${process.debugPort}`]
+  });
+
   console.log('forked worker should have --debug-port, with offset = 2');
   cluster.fork({
     portSet: process.debugPort + 2