diff --git a/toolkit/mozapps/update/content/updates.xul b/toolkit/mozapps/update/content/updates.xul
index 140375b04d2d..561fe9ed03f1 100644
--- a/toolkit/mozapps/update/content/updates.xul
+++ b/toolkit/mozapps/update/content/updates.xul
@@ -191,7 +191,7 @@
     </vbox>
   </wizardpage>
 
-  <wizardpage id="downloading" pageid="downloading" next="finished"
+  <wizardpage id="downloading" pageid="downloading"
               object="gDownloadingPage" onextra1="gDownloadingPage.onHide();"
               onpageshow="gDownloadingPage.onPageShow();">
     <updateheader label="&downloadPage.title;"/>
diff --git a/toolkit/mozapps/update/test/chrome/test_0083_error_patchApplyFailure_partial_complete.xul b/toolkit/mozapps/update/test/chrome/test_0083_error_patchApplyFailure_partial_complete.xul
index b56de4a9f0f3..c03fe3104cc1 100644
--- a/toolkit/mozapps/update/test/chrome/test_0083_error_patchApplyFailure_partial_complete.xul
+++ b/toolkit/mozapps/update/test/chrome/test_0083_error_patchApplyFailure_partial_complete.xul
@@ -62,9 +62,12 @@ SimpleTest.waitForExplicitFinish();
 function test01() {
   ok(true, "Entering test01 - test preparation");
 
+  // Specify the url to update.sjs with a slowDownloadMar param so the ui can
+  // load before the download completes.
+  var slowDownloadURL = URL_UPDATE + "?slowDownloadMar=1";
   var patches = getLocalPatchString("partial", null, null, null, null, null,
                                     STATE_PENDING) +
-                getLocalPatchString("complete");
+                getLocalPatchString("complete", slowDownloadURL);
   var updates = getLocalUpdateString(patches);
 
   writeUpdatesToXMLFile(getLocalUpdatesXMLString(updates), true);
@@ -100,20 +103,32 @@ function test02() {
   ok(gDocElem.getButton("cancel").disabled, "cancel button should be disabled");
 
   gNextFunc = test03;
+  gPageId = PAGEID_DOWNLOADING;
+  addPageShowListener();
+  // go forward to the downloading page
+  gDocElem.getButton("next").click();
+}
+
+/**
+ * downloading page
+ */
+function test03() {
+  ok(true, "Entering test12 - downloading page");
+
+  is(gDocElem.currentPage.pageid, PAGEID_DOWNLOADING,
+     "Page ID should be " + PAGEID_DOWNLOADING);
+
+  gNextFunc = test04;
   gPageId = PAGEID_FINISHED;
   addPageShowListener();
-  // Clicking next will immediately go forward to the finished page if the
-  // download has already finished or it will go to downloading page and then 
-  // automatically go forward to the finished page after the download has
-  // finished.
-  gDocElem.getButton("next").click();
+  // The downloading page will automatically go to the finish page.
 }
 
 /**
  * finished page
  */
-function test03() {
-  ok(true, "Entering test03 - finished page");
+function test04() {
+  ok(true, "Entering test04 - finished page");
 
   is(gDocElem.currentPage.pageid, PAGEID_FINISHED,
      "Page ID should be " + PAGEID_FINISHED);
diff --git a/toolkit/mozapps/update/test/chrome/test_0084_error_patchApplyFailure_verify_failed.xul b/toolkit/mozapps/update/test/chrome/test_0084_error_patchApplyFailure_verify_failed.xul
index 9b1055193965..653211801c6a 100644
--- a/toolkit/mozapps/update/test/chrome/test_0084_error_patchApplyFailure_verify_failed.xul
+++ b/toolkit/mozapps/update/test/chrome/test_0084_error_patchApplyFailure_verify_failed.xul
@@ -62,9 +62,12 @@ SimpleTest.waitForExplicitFinish();
 function test01() {
   ok(true, "Entering test01 - test preparation");
 
+  // Specify the url to update.sjs with a slowDownloadMar param so the ui can
+  // load before the download completes.
+  var slowDownloadURL = URL_UPDATE + "?slowDownloadMar=1";
   var patches = getLocalPatchString("partial", null, null, null, null, null,
                                     STATE_PENDING) +
-                getLocalPatchString("complete", null, "MD5",
+                getLocalPatchString("complete", slowDownloadURL, "MD5",
                                     "1234cd43a1c77e30191c53a329a3f99d");
 
   var updates = getLocalUpdateString(patches);
@@ -102,20 +105,32 @@ function test02() {
   ok(gDocElem.getButton("cancel").disabled, "cancel button should be disabled");
 
   gNextFunc = test03;
+  gPageId = PAGEID_DOWNLOADING;
+  addPageShowListener();
+  // go forward to the downloading page
+  gDocElem.getButton("next").click();
+}
+
+/**
+ * downloading page
+ */
+function test03() {
+  ok(true, "Entering test12 - downloading page");
+
+  is(gDocElem.currentPage.pageid, PAGEID_DOWNLOADING,
+     "Page ID should be " + PAGEID_DOWNLOADING);
+
+  gNextFunc = test04;
   gPageId = PAGEID_ERRORS;
   addPageShowListener();
-  // Clicking next will go forward to the finished page if the download has
-  // already finished or it will go to the downloading page and then
-  // automatically go forward to the finished page after the download has
-  // finished.
-  gDocElem.getButton("next").click();
+  // The downloading page will automatically go to the errors page.
 }
 
 /**
  * errors page
  */
-function test03() {
-  ok(true, "Entering test03 - errors page");
+function test04() {
+  ok(true, "Entering test04 - errors page");
 
   is(gDocElem.currentPage.pageid, PAGEID_ERRORS,
      "Page ID should be " + PAGEID_ERRORS);
diff --git a/toolkit/mozapps/update/test/chrome/update.sjs b/toolkit/mozapps/update/test/chrome/update.sjs
index 16465fa1020d..442523f99997 100644
--- a/toolkit/mozapps/update/test/chrome/update.sjs
+++ b/toolkit/mozapps/update/test/chrome/update.sjs
@@ -19,6 +19,31 @@ function handleRequest(request, response) {
   response.setStatusLine(request.httpVersion, statusCode, statusReason);
   response.setHeader("Cache-Control", "no-cache", false);
 
+  // When a mar download is started by the update service it can finish
+  // downloading before the ui has loaded. By specifying a serviceURL for the
+  // update patch that points to this file and has a slowDownloadMar param the
+  // mar will be downloaded asynchronously which will allow the ui to load
+  // before the download completes.
+  if (params.slowDownloadMar) {
+    response.processAsync();
+    response.setHeader("Content-Length", "775");
+    var marFile = AUS_Cc["@mozilla.org/file/directory_service;1"].
+                  getService(AUS_Ci.nsIProperties).
+                  get("CurWorkD", AUS_Ci.nsILocalFile);
+    var path = URL_PATH + "empty.mar";
+    var pathParts = path.split("/");
+    for(var i = 0; i < pathParts.length; ++i)
+      marFile.append(pathParts[i]);
+    var contents = readFileBytes(marFile);
+    var timer = AUS_Cc["@mozilla.org/timer;1"].
+                createInstance(AUS_Ci.nsITimer);
+    timer.initWithCallback(function() {
+      response.write(contents);
+      response.finish();
+    }, 2000, AUS_Ci.nsITimer.TYPE_ONE_SHOT);
+    return;
+  }
+
   if (params.uiURL) {
     var remoteType = "";
     if (!params.remoteNoTypeAttr &&