diff --git a/lib/_debugger.js b/lib/_debugger.js
index 00de2b1e70..c3f0631fad 100644
--- a/lib/_debugger.js
+++ b/lib/_debugger.js
@@ -25,7 +25,7 @@ var util = require('util'),
     vm = require('vm'),
     repl = require('repl'),
     inherits = util.inherits,
-    spawn = require('child_process').spawn;
+    fork = require('child_process').fork;
 
 exports.start = function(argv, stdin, stdout) {
   argv || (argv = process.argv.slice(2));
@@ -39,7 +39,7 @@ exports.start = function(argv, stdin, stdout) {
   stdin = stdin || process.openStdin();
   stdout = stdout || process.stdout;
 
-  var args = ['--debug-brk'].concat(argv),
+  var args = argv,
       interface = new Interface(stdin, stdout, args);
 
   stdin.resume();
@@ -169,6 +169,8 @@ function Client() {
   this.scripts = {};
   this.breakpoints = [];
 
+  this.isolates = process.features.isolates;
+
   // Note that 'Protocol' requires strings instead of Buffers.
   socket.setEncoding('utf8');
   socket.on('data', function(d) {
@@ -1595,20 +1597,51 @@ Interface.prototype.trySpawn = function(cb) {
     }
   }
 
-  if (!this.child) {
-    this.child = spawn(process.execPath, this.args);
+  var client = self.client = new Client(),
+      connectionAttempts = 0;
 
-    this.child.stdout.on('data', this.childPrint.bind(this));
-    this.child.stderr.on('data', this.childPrint.bind(this));
+  if (!this.child) {
+    if (client.isolates) {
+      this.child = fork(this.args.shift(), this.args, {
+        thread: true,
+        debug: function(d) {
+          d.onmessage = function(event) {
+            client._onResponse({
+              headers: {},
+              body: JSON.parse(event)
+            });
+          };
+
+          // Monkey patch client to send requests directly to debugger
+          client.req = function(req, cb) {
+            req.type = 'request';
+            cb.request_seq = req.seq = this.protocol.reqSeq++;
+            this._reqCallbacks.push(cb);
+
+            d.write(JSON.stringify(req));
+          };
+
+          client.emit('ready');
+
+          client._onResponse({
+            headers: { Type: 'connect' },
+            body: {}
+          });
+        },
+        debugBrk: true
+      });
+      this.child.kill = function() {
+        self.error('isolate.kill is not implemented yet!');
+      };
+    } else {
+      this.child = fork('--debug-brk', this.args);
+    }
   }
 
   this.pause();
 
-  var client = self.client = new Client(),
-      connectionAttempts = 0;
-
   client.once('ready', function() {
-    self.stdout.write(' ok\n');
+    if (!client.isolates) self.stdout.write(' ok\n');
 
     // Restore breakpoints
     breakpoints.forEach(function(bp) {
@@ -1656,11 +1689,14 @@ Interface.prototype.trySpawn = function(cb) {
   function attemptConnect() {
     ++connectionAttempts;
     self.stdout.write('.');
+
     client.connect(port, host);
   }
 
-  setTimeout(function() {
-    self.print('connecting..', true);
-    attemptConnect();
-  }, 50);
+  if (!client.isolates) {
+    setTimeout(function() {
+      self.print('connecting..', true);
+      attemptConnect();
+    }, 50);
+  }
 };
diff --git a/lib/child_process.js b/lib/child_process.js
index 5a3374cdaf..f72b78b241 100644
--- a/lib/child_process.js
+++ b/lib/child_process.js
@@ -361,7 +361,8 @@ var spawn = exports.spawn = function(file, args, options) {
     windowsVerbatimArguments: !!(options && options.windowsVerbatimArguments),
     envPairs: envPairs,
     customFds: options ? options.customFds : null,
-    stdinStream: options ? options.stdinStream : null
+    stdinStream: options ? options.stdinStream : null,
+    options: options
   });
 
   return child;
@@ -538,7 +539,7 @@ Isolate.prototype.spawn = function(options) {
   var self = this;
 
   if (self._handle) throw new Error('Isolate already running.');
-  self._handle = isolates.create(options.args);
+  self._handle = isolates.create(options.args, options.options);
   if (!self._handle) throw new Error('Cannot create isolate.');
 
   self._handle.onmessage = function(msg) {