diff --git a/testing/marionette/client/marionette/emulator.py b/testing/marionette/client/marionette/emulator.py
index 074f61608ed8..b5c5fcbcd1cb 100644
--- a/testing/marionette/client/marionette/emulator.py
+++ b/testing/marionette/client/marionette/emulator.py
@@ -538,7 +538,7 @@ window.addEventListener('mozbrowserloadend', function loaded(aEvent) {
                 sock.connect(('localhost', self.marionette_port))
                 data = sock.recv(16)
                 sock.close()
-                if '"from"' in data:
+                if ':' in data:
                     return True
             except:
                 import traceback
diff --git a/testing/marionette/client/marionette/marionette.py b/testing/marionette/client/marionette/marionette.py
index 3e9e2d6b047e..7c36643e62cb 100644
--- a/testing/marionette/client/marionette/marionette.py
+++ b/testing/marionette/client/marionette/marionette.py
@@ -586,7 +586,7 @@ class Marionette(object):
                 sock.connect((self.host, self.port))
                 data = sock.recv(16)
                 sock.close()
-                if '"from"' in data:
+                if ':' in data:
                     time.sleep(5)
                     return True
             except socket.error:
diff --git a/testing/marionette/components/marionettecomponent.js b/testing/marionette/components/marionettecomponent.js
index acf32a94051e..ce6d415fc54a 100644
--- a/testing/marionette/components/marionettecomponent.js
+++ b/testing/marionette/components/marionettecomponent.js
@@ -6,6 +6,7 @@ this.CC = Components.Constructor;
 this.Cc = Components.classes;
 this.Ci = Components.interfaces;
 this.Cu = Components.utils;
+this.Cr = Components.results;
 
 const MARIONETTE_CONTRACTID = "@mozilla.org/marionette;1";
 const MARIONETTE_CID = Components.ID("{786a1369-dca5-4adc-8486-33d23c88010a}");
diff --git a/testing/marionette/marionette-server.js b/testing/marionette/marionette-server.js
index d2c59907bd08..d6f64a3b31c6 100644
--- a/testing/marionette/marionette-server.js
+++ b/testing/marionette/marionette-server.js
@@ -38,7 +38,7 @@ let appName = Services.appinfo.name;
 let { devtools } = Cu.import("resource://gre/modules/devtools/Loader.jsm", {});
 let DevToolsUtils = devtools.require("devtools/toolkit/DevToolsUtils.js");
 this.DevToolsUtils = DevToolsUtils;
-loader.loadSubScript("resource://gre/modules/devtools/server/transport.js");
+loader.loadSubScript("resource://gre/modules/devtools/transport/transport.js");
 
 let bypassOffline = false;
 let qemu = "0";
@@ -202,7 +202,7 @@ MarionetteServerConnection.prototype = {
    */
   sendAsync: function MDA_sendAsync(name, values, commandId, ignoreFailure) {
     let success = true;
-    if (values instanceof Object && commandId) {
+    if (commandId) {
       values.command_id = commandId;
     }
     if (this.curBrowser.frameManager.currentRemoteFrame !== null) {
diff --git a/testing/marionette/transport/marionette_transport/transport.py b/testing/marionette/transport/marionette_transport/transport.py
index 41da169d881b..e28d16ff83a0 100644
--- a/testing/marionette/transport/marionette_transport/transport.py
+++ b/testing/marionette/transport/marionette_transport/transport.py
@@ -45,11 +45,13 @@ class MarionetteTransport(object):
         """
         assert(self.sock)
         response = self.sock.recv(10)
+        initial_size = len(response)
         sep = response.find(':')
         length = response[0:sep]
         if length != '':
             response = response[sep + 1:]
-            response += self._recv_n_bytes(int(length) + 1 + len(length) - 10)
+            remaining_size = int(length) + 1 + len(length) - initial_size
+            response += self._recv_n_bytes(remaining_size)
             return json.loads(response)
         else:
             raise IOError(self.connection_lost_msg)