--- a/testing/marionette/client/marionette/marionette.py
+++ b/testing/marionette/client/marionette/marionette.py
@@ -416,54 +416,51 @@ class Marionette(object):
                     unwrapped = HTMLElement(self, value[key])
                 else:
                     unwrapped[key] = self.unwrapValue(value[key])
         else:
             unwrapped = value
 
         return unwrapped
 
-    def execute_js_script(self, script, script_args=None, async=True, new_sandbox=True, special_powers=False, script_timeout=None):
+    def execute_js_script(self, script, script_args=None, async=True, new_sandbox=True, special_powers=False):
         if script_args is None:
             script_args = []
         args = self.wrapArguments(script_args)
         response = self._send_message('executeJSScript',
                                       'value',
                                       value=script,
                                       args=args,
                                       async=async,
                                       newSandbox=new_sandbox,
-                                      specialPowers=special_powers, 
-                                      scriptTimeout=script_timeout)
+                                      specialPowers=special_powers)
         return self.unwrapValue(response)
 
-    def execute_script(self, script, script_args=None, new_sandbox=True, special_powers=False, script_timeout=None):
+    def execute_script(self, script, script_args=None, new_sandbox=True, special_powers=False):
         if script_args is None:
             script_args = []
         args = self.wrapArguments(script_args)
         response = self._send_message('executeScript',
                                      'value',
                                       value=script,
                                       args=args,
                                       newSandbox=new_sandbox,
-                                      specialPowers=special_powers,
-                                      scriptTimeout=script_timeout)
+                                      specialPowers=special_powers)
         return self.unwrapValue(response)
 
-    def execute_async_script(self, script, script_args=None, new_sandbox=True, special_powers=False, script_timeout=None):
+    def execute_async_script(self, script, script_args=None, new_sandbox=True, special_powers=False):
         if script_args is None:
             script_args = []
         args = self.wrapArguments(script_args)
         response = self._send_message('executeAsyncScript',
                                       'value',
                                       value=script,
                                       args=args,
                                       newSandbox=new_sandbox,
-                                      specialPowers=special_powers,
-                                      scriptTimeout=script_timeout)
+                                      specialPowers=special_powers)
         return self.unwrapValue(response)
 
     def find_element(self, method, target, id=None):
         kwargs = { 'value': target, 'using': method }
         if id:
             kwargs['element'] = id
         response = self._send_message('findElement', 'value', **kwargs)
         element = HTMLElement(self, response)

--- a/testing/marionette/client/marionette/tests/unit/test_execute_async_script.py
+++ b/testing/marionette/client/marionette/tests/unit/test_execute_async_script.py
@@ -14,20 +14,16 @@ class TestExecuteAsyncContent(Marionette
         self.assertEqual(1, self.marionette.execute_async_script("arguments[arguments.length-1](1);"))
 
     def test_execute_async_ours(self):
         self.assertEqual(1, self.marionette.execute_async_script("marionetteScriptFinished(1);"))
 
     def test_execute_async_timeout(self):
         self.assertRaises(ScriptTimeoutException, self.marionette.execute_async_script, "var x = 1;")
 
-    def test_execute_async_unique_timeout(self):
-        self.assertEqual(1, self.marionette.execute_async_script("setTimeout(function() {marionetteScriptFinished(1);}, 2000);", script_timeout=5000))
-        self.assertRaises(ScriptTimeoutException, self.marionette.execute_async_script, "setTimeout(function() {marionetteScriptFinished(1);}, 2000);")
-
     def test_no_timeout(self):
         self.marionette.set_script_timeout(10000)
         self.assertTrue(self.marionette.execute_async_script("""
             var callback = arguments[arguments.length - 1];
             setTimeout(function() { callback(true); }, 500);
             """))
 
     @skip_if_b2g
@@ -103,8 +99,9 @@ class TestExecuteAsyncChrome(TestExecute
     def test_execute_permission(self):
         self.assertEqual(1, self.marionette.execute_async_script("""
 var c = Components.classes;
 marionetteScriptFinished(1);
 """))
 
     def test_sandbox_reuse(self):
         pass
+

--- a/testing/marionette/marionette-actors.js
+++ b/testing/marionette/marionette-actors.js
@@ -664,20 +664,20 @@ MarionetteDriverActor.prototype = {
    * @param boolean directInject
    *        If true, then the script will be run as is,
    *        and not as a function body (as you would
    *        do using the WebDriver spec)
    * @param boolean async
    *        True if the script is asynchronous
    */
   executeScriptInSandbox: function MDA_executeScriptInSandbox(sandbox, script,
-     directInject, async, command_id, timeout) {
+     directInject, async, command_id) {
 
     if (directInject && async &&
-        (timeout == null || timeout == 0)) {
+        (this.scriptTimeout == null || this.scriptTimeout == 0)) {
       this.sendError("Please set a timeout", 21, null, command_id);
       return;
     }
 
     if (this.importedScripts.exists()) {
       let stream = Cc["@mozilla.org/network/file-input-stream;1"].  
                     createInstance(Ci.nsIFileInputStream);
       stream.init(this.importedScripts, -1, 0, 0);
@@ -706,37 +706,36 @@ MarionetteDriverActor.prototype = {
    * @param object aRequest
    *        'value' member is the script to run
    *        'args' member holds the arguments to the script
    * @param boolean directInject
    *        if true, it will be run directly and not as a 
    *        function body
    */
   execute: function MDA_execute(aRequest, directInject) {
-    let timeout = aRequest.scriptTimeout ? aRequest.scriptTimeout : this.scriptTimeout;
     let command_id = this.command_id = this.getCommandId();
     this.logRequest("execute", aRequest);
     if (aRequest.newSandbox == undefined) {
       //if client does not send a value in newSandbox, 
       //then they expect the same behaviour as webdriver
       aRequest.newSandbox = true;
     }
     if (this.context == "content") {
       this.sendAsync("executeScript", {value: aRequest.value,
                                        args: aRequest.args,
                                        newSandbox: aRequest.newSandbox,
-                                       timeout: timeout,
+                                       timeout: this.scriptTimeout,
                                        command_id: command_id});
       return;
     }
 
     let curWindow = this.getCurrentWindow();
     let marionette = new Marionette(this, curWindow, "chrome",
                                     this.marionetteLog, this.marionettePerf,
-                                    timeout, this.testName);
+                                    this.scriptTimeout, this.testName);
     let _chromeSandbox = this.createExecuteSandbox(curWindow,
                                                    marionette,
                                                    aRequest.args,
                                                    aRequest.specialPowers);
     if (!_chromeSandbox)
       return;
 
     try {
@@ -750,17 +749,17 @@ MarionetteDriverActor.prototype = {
       }
       else {
         script = "let func = function() {" +
                        aRequest.value + 
                      "};" +
                      "func.apply(null, __marionetteParams);";
       }
       this.executeScriptInSandbox(_chromeSandbox, script, directInject,
-                                  false, command_id, timeout);
+                                  false, command_id);
     }
     catch (e) {
       this.sendError(e.name + ': ' + e.message, 17, e.stack, command_id);
     }
   },
 
   /**
    * Set the timeout for asynchronous script execution
@@ -784,17 +783,16 @@ MarionetteDriverActor.prototype = {
    * execute pure JS script. Used to execute 'mochitest'-style Marionette tests.
    *
    * @param object aRequest
    *        'value' member holds the script to execute
    *        'args' member holds the arguments to the script
    *        'timeout' member will be used as the script timeout if it is given
    */
   executeJSScript: function MDA_executeJSScript(aRequest) {
-    let timeout = aRequest.scriptTimeout ? aRequest.scriptTimeout : this.scriptTimeout;
     let command_id = this.command_id = this.getCommandId();
     //all pure JS scripts will need to call Marionette.finish() to complete the test.
     if (aRequest.newSandbox == undefined) {
       //if client does not send a value in newSandbox, 
       //then they expect the same behaviour as webdriver
       aRequest.newSandbox = true;
     }
     if (this.context == "chrome") {
@@ -805,17 +803,17 @@ MarionetteDriverActor.prototype = {
         this.execute(aRequest, true);
       }
     }
     else {
       this.sendAsync("executeJSScript", { value: aRequest.value,
                                           args: aRequest.args,
                                           newSandbox: aRequest.newSandbox,
                                           async: aRequest.async,
-                                          timeout: timeout,
+                                          timeout: this.scriptTimeout,
                                           command_id: command_id });
    }
   },
 
   /**
    * This function is used by executeAsync and executeJSScript to execute a script
    * in a sandbox. 
    * 
@@ -826,41 +824,39 @@ MarionetteDriverActor.prototype = {
    * @param object aRequest
    *        'value' member holds the script to execute
    *        'args' member holds the arguments for the script
    * @param boolean directInject
    *        if true, it will be run directly and not as a 
    *        function body
    */
   executeWithCallback: function MDA_executeWithCallback(aRequest, directInject) {
-    let timeout = aRequest.scriptTimeout ? aRequest.scriptTimeout : this.scriptTimeout;
     let command_id = this.command_id = this.getCommandId();
     if (aRequest.newSandbox == undefined) {
       //if client does not send a value in newSandbox, 
       //then they expect the same behaviour as webdriver
       aRequest.newSandbox = true;
     }
 
     if (this.context == "content") {
       this.sendAsync("executeAsyncScript", {value: aRequest.value,
                                             args: aRequest.args,
                                             id: this.command_id,
                                             newSandbox: aRequest.newSandbox,
-                                            timeout: timeout,
+                                            timeout: this.scriptTimeout,
                                             command_id: command_id});
       return;
     }
 
     let curWindow = this.getCurrentWindow();
     let original_onerror = curWindow.onerror;
     let that = this;
-    that.timeout = timeout;
     let marionette = new Marionette(this, curWindow, "chrome",
                                     this.marionetteLog, this.marionettePerf,
-                                    timeout, this.testName);
+                                    this.scriptTimeout, this.testName);
     marionette.command_id = this.command_id;
 
     function chromeAsyncReturnFunc(value, status) {
       if (that._emu_cbs && Object.keys(that._emu_cbs).length) {
         value = "Emulator callback still pending when finish() called";
         status = 500;
         that._emu_cbs = null;
       }
@@ -901,17 +897,17 @@ MarionetteDriverActor.prototype = {
       return;
 
     try {
 
       this.timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
       if (this.timer != null) {
         this.timer.initWithCallback(function() {
           chromeAsyncReturnFunc("timed out", 28);
-        }, that.timeout, Ci.nsITimer.TYPE_ONESHOT);
+        }, that.scriptTimeout, Ci.nsITimer.TYPE_ONESHOT);
       }
 
       _chromeSandbox.returnFunc = chromeAsyncReturnFunc;
       _chromeSandbox.finish = chromeAsyncFinish;
 
       let script;
       if (directInject) {
         script = aRequest.value;
@@ -919,17 +915,17 @@ MarionetteDriverActor.prototype = {
       else {
         script =  '__marionetteParams.push(returnFunc);'
                 + 'let marionetteScriptFinished = returnFunc;'
                 + 'let __marionetteFunc = function() {' + aRequest.value + '};'
                 + '__marionetteFunc.apply(null, __marionetteParams);';
       }
 
       this.executeScriptInSandbox(_chromeSandbox, script, directInject,
-                                  true, command_id, timeout);
+                                  true, command_id);
     } catch (e) {
       chromeAsyncReturnFunc(e.name + ": " + e.message, 17);
     }
   },
 
   /**
    * Navigates to given url
    *