diff -r 000000000000 -r 6474c204b198 browser/components/customizableui/test/browser_956602_remove_special_widget.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/customizableui/test/browser_956602_remove_special_widget.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,31 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+
+// Adding a separator and then dragging it out of the navbar shouldn't throw
+add_task(function() {
+  try {
+    let navbar = document.getElementById("nav-bar");
+    let separatorSelector = "toolbarseparator[id^=customizableui-special-separator]";
+    ok(!navbar.querySelector(separatorSelector), "Shouldn't be a separator in the navbar");
+    CustomizableUI.addWidgetToArea('separator', 'nav-bar');
+    yield startCustomizing();
+    let separator = navbar.querySelector(separatorSelector);
+    ok(separator, "There should be a separator in the navbar now.");
+    let palette = document.getElementById("customization-palette");
+    simulateItemDrag(separator, palette);
+    ok(!palette.querySelector(separatorSelector), "No separator in the palette.");
+  } catch (ex) {
+    Cu.reportError(ex);
+    ok(false, "Shouldn't throw an exception moving an item to the navbar.");
+  } finally {
+    yield endCustomizing();
+  }
+});
+
+add_task(function asyncCleanup() {
+  resetCustomization();
+});