diff --git a/browser/components/wintaskbar/test/browser_taskbar_preview.js b/browser/components/wintaskbar/test/browser_taskbar_preview.js
index 528105cb2579..b6139dbec8c1 100644
--- a/browser/components/wintaskbar/test/browser_taskbar_preview.js
+++ b/browser/components/wintaskbar/test/browser_taskbar_preview.js
@@ -11,13 +11,15 @@ function test() {
   if (!isWin7OrHigher)
     return;
 
+  const ENABLE_PREF_NAME = "browser.taskbar.previews.enable";
+
   let temp = {};
   Cu.import("resource://gre/modules/WindowsPreviewPerTab.jsm", temp);
   let AeroPeek = temp.AeroPeek;
 
   waitForExplicitFinish();
 
-  gPrefService.setBoolPref("aeropeek.enable", true);
+  gPrefService.setBoolPref(ENABLE_PREF_NAME, true);
 
   is(1, AeroPeek.windows.length, "Got the expected number of windows");
 
@@ -32,13 +34,13 @@ function test() {
   for each (let preview in AeroPeek.previews)
     ok(preview.visible, "Preview is shown as expected");
 
-  gPrefService.setBoolPref("aeropeek.enable", false);
+  gPrefService.setBoolPref(ENABLE_PREF_NAME, false);
   checkPreviews(4, "Previews are unchanged when disabling");
 
   for each (let preview in AeroPeek.previews)
     ok(!preview.visible, "Preview is not shown as expected after disabling");
 
-  gPrefService.setBoolPref("aeropeek.enable", true);
+  gPrefService.setBoolPref(ENABLE_PREF_NAME, true);
   checkPreviews(4, "Previews are unchanged when re-enabling");
   for each (let preview in AeroPeek.previews)
     ok(preview.visible, "Preview is shown as expected after re-enabling");
@@ -92,7 +94,7 @@ function test() {
   getPreviewForTab(gBrowser.mTabs[1]).controller.onClose();
   checkPreviews(1);
 
-  gPrefService.clearUserPref("aeropeek.enable");
+  gPrefService.clearUserPref(ENABLE_PREF_NAME);
 
   finish();
 
diff --git a/widget/src/windows/TaskbarTabPreview.cpp b/widget/src/windows/TaskbarTabPreview.cpp
index abfd837c7607..c6d08359057c 100644
--- a/widget/src/windows/TaskbarTabPreview.cpp
+++ b/widget/src/windows/TaskbarTabPreview.cpp
@@ -126,7 +126,7 @@ TaskbarTabPreview::SetIcon(imgIContainer *icon) {
 
 NS_IMETHODIMP
 TaskbarTabPreview::GetIcon(imgIContainer **icon) {
-  NS_ADDREF(*icon = mIconImage);
+  NS_IF_ADDREF(*icon = mIconImage);
   return NS_OK;
 }
 
diff --git a/widget/tests/taskbar_previews.xul b/widget/tests/taskbar_previews.xul
index e7b0487f22f0..11442b4d84f1 100644
--- a/widget/tests/taskbar_previews.xul
+++ b/widget/tests/taskbar_previews.xul
@@ -82,6 +82,7 @@
       let tabP = taskbar.createTaskbarTabPreview(docShell, controller);
       isnot(tabP, null, "Tab preview is not null");
       is(tabP.controller.wrappedJSObject, controller, "Controllers match");
+      is(tabP.icon, null, "Default icon is null (windows default)");
       tabP.icon = null;
       tabP.move(null);
       try {