--- a/testing/marionette/driver.js
+++ b/testing/marionette/driver.js
@@ -653,17 +653,17 @@ GeckoDriver.prototype.setUpProxy = funct
           if (proxy.socksVersion) {
             Preferences.set("network.proxy.socks_version", proxy.socksVersion);
           }
         }
         break;
 
       case "PAC":
         Preferences.set("network.proxy.type", 2);
-        Preferences.set("network.proxy.autoconfig_url", proxy.pacUrl);
+        Preferences.set("network.proxy.autoconfig_url", proxy.proxyAutoconfigUrl);
         break;
 
       case "AUTODETECT":
         Preferences.set("network.proxy.type", 4);
         break;
 
       case "SYSTEM":
         Preferences.set("network.proxy.type", 5);

--- a/testing/marionette/harness/marionette/tests/unit/test_proxy.py
+++ b/testing/marionette/harness/marionette/tests/unit/test_proxy.py
@@ -61,31 +61,31 @@ class TestProxy(MarionetteTestCase):
         self.assertEqual(result["proxyType"], 5)
 
     def test_we_can_set_a_pac_proxy(self):
         url = "http://marionette.test"
         capabilities = {"requiredCapabilities":
                             {
                                 "proxy":{
                                     "proxyType": "pac",
-                                    "pacUrl": url,
+                                    "proxyAutoconfigUrl": url,
                                 }
                             }
                         }
         self.marionette.start_session(capabilities)
         result = None
         with self.marionette.using_context('chrome'):
             result = self.marionette.execute_script("""return {
                 "proxyType" : Services.prefs.getIntPref('network.proxy.type'),
-                "pacUrl" : Services.prefs.getCharPref('network.proxy.autoconfig_url'),
+                "proxyAutoconfigUrl" : Services.prefs.getCharPref('network.proxy.autoconfig_url'),
                 }
             """)
 
         self.assertEqual(result["proxyType"], 2)
-        self.assertEqual(result["pacUrl"], url, 'pacUrl was not set')
+        self.assertEqual(result["proxyAutoconfigUrl"], url, 'proxyAutoconfigUrl was not set')
 
     def test_that_we_can_set_a_manual_proxy(self):
         port = 4444
         url = "http://marionette.test"
         capabilities = {"requiredCapabilities":
                             {
                                 "proxy":{
                                     "proxyType": "manual",