diff --git a/toolkit/mozapps/extensions/test/unit/test_bug509194.js b/toolkit/mozapps/extensions/test/unit/test_bug509194.js
new file mode 100644
index 00000000000..88361ae086a
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+++ b/toolkit/mozapps/extensions/test/unit/test_bug509194.js
@@ -0,0 +1,62 @@
+/* ***** 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
+ *      Dave Townsend <dtownsend@oxymoronical.com>.
+ *
+ * Portions created by the Initial Developer are Copyright (C) 2009
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either 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 *****
+ */
+
+const ID = "{972ce4c6-7e08-4474-a285-3208198ce6fd}";
+
+function run_test()
+{
+  // Setup for test
+  createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "1");
+  startupEM();
+
+  var addon = gEM.getItemForID(ID);
+  // Some applications don't have the default theme defined
+  if (!addon)
+    return;
+
+  var iconURL = getManifestProperty(ID, "iconURL");
+  var location = gEM.getInstallLocation(ID);
+  var file = location.getItemFile(ID, "icon.png");
+  var ioservice = Components.classes["@mozilla.org/network/io-service;1"]
+                            .getService(Components.interfaces.nsIIOService);
+  var uri = ioservice.newURI(iconURL, null, null);
+  uri.QueryInterface(Components.interfaces.nsIFileURL);
+  do_check_true(uri.file.equals(file));
+
+  shutdownEM();
+}