diff --git a/browser/components/shell/Makefile.in b/browser/components/shell/Makefile.in
index d0c719f6b93..ae69168d65e 100644
--- a/browser/components/shell/Makefile.in
+++ b/browser/components/shell/Makefile.in
@@ -44,4 +44,8 @@ include $(DEPTH)/config/autoconf.mk
 
 DIRS = public src
 
+ifdef MOZ_MOCHITEST
+DIRS += test
+endif
+
 include $(topsrcdir)/config/rules.mk
diff --git a/browser/components/shell/src/nsGNOMEShellService.cpp b/browser/components/shell/src/nsGNOMEShellService.cpp
index 88bfd7fb4d5..0ff75cf8485 100644
--- a/browser/components/shell/src/nsGNOMEShellService.cpp
+++ b/browser/components/shell/src/nsGNOMEShellService.cpp
@@ -365,7 +365,6 @@ WriteImage(const nsCString& aPath, gfxIImageFrame* aImage)
 
   gboolean res = gdk_pixbuf_save(pixbuf, aPath.get(), "png", NULL, NULL);
 
-  aImage->UnlockImageData();
   g_object_unref(pixbuf);
   return res ? NS_OK : NS_ERROR_FAILURE;
 #endif
diff --git a/browser/components/shell/test/Makefile.in b/browser/components/shell/test/Makefile.in
new file mode 100644
index 00000000000..4724e935411
--- /dev/null
+++ b/browser/components/shell/test/Makefile.in
@@ -0,0 +1,51 @@
+# ***** BEGIN LICENSE BLOCK *****
+# Version: MPL 1.1/GPL 2.0/LGPL 2.1
+#
+# The contents of this file are subject to the Mozilla Public License Version
+# 1.1 (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+# http://www.mozilla.org/MPL/
+#
+# Software distributed under the License is distributed on an "AS IS" basis,
+# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+# for the specific language governing rights and limitations under the
+# License.
+#
+# The Original Code is mozilla.org code.
+#
+# The Initial Developer of the Original Code is
+# Sylvain Pasche.
+# Portions created by the Initial Developer are Copyright (C) 2008
+# the Initial Developer. All Rights Reserved.
+#
+# Contributor(s):
+#
+# Alternatively, the contents of this file may be used under the terms of
+# either of the GNU General Public License Version 2 or later (the "GPL"),
+# or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+# in which case the provisions of the GPL or the LGPL are applicable instead
+# of those above. If you wish to allow use of your version of this file only
+# under the terms of either the GPL or the LGPL, and not to allow others to
+# use your version of this file under the terms of the MPL, indicate your
+# decision by deleting the provisions above and replace them with the notice
+# and other provisions required by the GPL or the LGPL. If you do not delete
+# the provisions above, a recipient may use your version of this file under
+# the terms of any one of the MPL, the GPL or the LGPL.
+#
+# ***** END LICENSE BLOCK *****
+
+DEPTH		= ../../../..
+topsrcdir	= @top_srcdir@
+srcdir		= @srcdir@
+VPATH		= @srcdir@
+relativesrcdir  = browser/components/shell/test
+
+include $(DEPTH)/config/autoconf.mk
+
+include $(topsrcdir)/config/rules.mk
+
+_BROWSER_TEST_FILES = browser_420786.js \
+	$(NULL)
+
+libs:: $(_BROWSER_TEST_FILES)
+	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/browser/$(relativesrcdir)
diff --git a/browser/components/shell/test/browser_420786.js b/browser/components/shell/test/browser_420786.js
new file mode 100644
index 00000000000..93e7aba4e81
--- /dev/null
+++ b/browser/components/shell/test/browser_420786.js
@@ -0,0 +1,98 @@
+const Ci = Components.interfaces;
+const Cc = Components.classes;
+
+const DG_BACKGROUND = "/desktop/gnome/background"
+const DG_IMAGE_KEY = DG_BACKGROUND + "/picture_filename";
+const DG_OPTION_KEY = DG_BACKGROUND + "/picture_options";
+const DG_DRAW_BG_KEY = DG_BACKGROUND + "/draw_background";
+
+var testPage;
+
+function url(spec) {
+  var ios = Cc["@mozilla.org/network/io-service;1"].
+            getService(Ci.nsIIOService);
+  return ios.newURI(spec, null, null);
+}
+
+function onPageLoad() {
+  testPage.events.removeListener("load", onPageLoad);
+
+  var bs = Cc["@mozilla.org/intl/stringbundle;1"].
+           getService(Ci.nsIStringBundleService);
+  var brandName = bs.createBundle("chrome://branding/locale/brand.properties").
+                  GetStringFromName("brandShortName");
+
+  var dirSvc = Cc["@mozilla.org/file/directory_service;1"].
+               getService(Ci.nsIDirectoryServiceProvider);
+  var homeDir = dirSvc.getFile("Home", {});
+
+  var wpFile = homeDir.clone();
+  wpFile.append(brandName + "_wallpaper.png");
+
+  // Backup the existing wallpaper so that this test doesn't change the user's
+  // settings.
+  var wpFileBackup = homeDir.clone()
+  wpFileBackup.append(brandName + "_wallpaper.png.backup");
+
+  if (wpFileBackup.exists())
+    wpFileBackup.remove(false);
+
+  if (wpFile.exists())
+    wpFile.copyTo(null, wpFileBackup.leafName);
+
+  var shell = Cc["@mozilla.org/browser/shell-service;1"].
+              getService(Ci.nsIShellService);
+  var gconf = Cc["@mozilla.org/gnome-gconf-service;1"].
+              getService(Ci.nsIGConfService);
+
+  var prevImageKey = gconf.getString(DG_IMAGE_KEY);
+  var prevOptionKey = gconf.getString(DG_OPTION_KEY);
+  var prevDrawBgKey = gconf.getBool(DG_DRAW_BG_KEY);
+
+  var image = testPage.document.getElementsByTagName("img")[0];
+
+  function checkWallpaper(position, expectedGConfPosition) {
+    shell.setDesktopBackground(image, position);
+    ok(wpFile.exists(), "Wallpaper was written to disk");
+    is(gconf.getString(DG_IMAGE_KEY), wpFile.path,
+       "Wallpaper file GConf key is correct");
+    is(gconf.getString(DG_OPTION_KEY), expectedGConfPosition,
+       "Wallpaper position GConf key is correct");
+  }
+
+  checkWallpaper(Ci.nsIShellService.BACKGROUND_TILE, "wallpaper");
+  checkWallpaper(Ci.nsIShellService.BACKGROUND_STRETCH, "stretched");
+  checkWallpaper(Ci.nsIShellService.BACKGROUND_CENTER, "centered");
+  checkWallpaper(Ci.nsIShellService.BACKGROUND_FILL, "centered");
+
+  // Restore GConf and wallpaper
+
+  gconf.setString(DG_IMAGE_KEY, prevImageKey);
+  gconf.setString(DG_OPTION_KEY, prevOptionKey);
+  gconf.setBool(DG_DRAW_BG_KEY, prevDrawBgKey);
+
+  wpFile.remove(false);
+  if (wpFileBackup.exists()) {
+   wpFileBackup.moveTo(null, wpFile.leafName);
+  }
+  testPage.close();
+  finish();
+}
+
+function test() {
+  var osString = Cc["@mozilla.org/xre/app-info;1"].
+                 getService(Ci.nsIXULRuntime).OS;
+
+  // This test is Linux specific for now
+  if (osString != "Linux") {
+    finish();
+    return;
+  }
+
+  testPage = Application.activeWindow.open(url("about:blank"));
+  testPage.events.addListener("load", onPageLoad);
+  testPage.load(url("about:logo"));
+  testPage.focus();
+
+  waitForExplicitFinish();
+}