diff --git a/lib/_debugger.js b/lib/_debugger.js
index 411db79d08..a5d3f6e872 100644
--- a/lib/_debugger.js
+++ b/lib/_debugger.js
@@ -25,7 +25,7 @@ exports.start = function(argv, stdin, stdout) {
   stdin = stdin || process.stdin;
   stdout = stdout || process.stdout;
 
-  const args = ['--debug-brk'].concat(argv);
+  const args = [`--debug-brk=${exports.port}`].concat(argv);
   const interface_ = new Interface(stdin, stdout, args);
 
   stdin.resume();
@@ -40,7 +40,7 @@ exports.start = function(argv, stdin, stdout) {
   });
 };
 
-exports.port = 5858;
+exports.port = process.debugPort;
 
 
 //
diff --git a/test/parallel/test-debug-port-numbers.js b/test/parallel/test-debug-port-numbers.js
new file mode 100644
index 0000000000..e21cb72f0a
--- /dev/null
+++ b/test/parallel/test-debug-port-numbers.js
@@ -0,0 +1,41 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const path = require('path');
+const spawn = require('child_process').spawn;
+
+const children = [];
+for (let i = 0; i < 4; i += 1) {
+  const port = common.PORT + i;
+  const args = [`--debug-port=${port}`, '--interactive', 'debug', __filename];
+  const child = spawn(process.execPath, args, { stdio: 'pipe' });
+  child.test = { port: port, stdout: '' };
+  child.stdout.setEncoding('utf8');
+  child.stdout.on('data', function(s) { child.test.stdout += s; update(); });
+  child.stdout.pipe(process.stdout);
+  child.stderr.pipe(process.stderr);
+  children.push(child);
+}
+
+function update() {
+  // Debugger prints relative paths except on Windows.
+  const filename = path.basename(__filename);
+
+  let ready = 0;
+  for (const child of children)
+    ready += RegExp(`break in .*?${filename}:1`).test(child.test.stdout);
+
+  if (ready === children.length)
+    for (const child of children)
+      child.kill();
+}
+
+process.on('exit', function() {
+  for (const child of children) {
+    const one = RegExp(`Debugger listening on port ${child.test.port}`);
+    const two = RegExp(`connecting to 127.0.0.1:${child.test.port}`);
+    assert(one.test(child.test.stdout));
+    assert(two.test(child.test.stdout));
+  }
+});