--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -22,16 +22,18 @@ XPCOMUtils.defineLazyModuleGetter(this, 
 XPCOMUtils.defineLazyGetter(this, "gWidgetsBundle", function() {
   const kUrl = "chrome://browser/locale/customizableui/customizableWidgets.properties";
   return Services.strings.createBundle(kUrl);
 });
 XPCOMUtils.defineLazyModuleGetter(this, "ShortcutUtils",
   "resource://gre/modules/ShortcutUtils.jsm");
 XPCOMUtils.defineLazyServiceGetter(this, "gELS",
   "@mozilla.org/eventlistenerservice;1", "nsIEventListenerService");
+XPCOMUtils.defineLazyModuleGetter(this, "LightweightThemeManager",
+                                  "resource://gre/modules/LightweightThemeManager.jsm");
 
 const kNSXUL = "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
 
 const kSpecialWidgetPfx = "customizableui-special-";
 
 const kPrefCustomizationState        = "browser.uiCustomization.state";
 const kPrefCustomizationAutoAdd      = "browser.uiCustomization.autoAdd";
 const kPrefCustomizationDebug        = "browser.uiCustomization.debug";
@@ -146,16 +148,17 @@ var gBuildWindows = new Map();
 var gNewElementCount = 0;
 var gGroupWrapperCache = new Map();
 var gSingleWrapperCache = new WeakMap();
 var gListeners = new Set();
 
 var gUIStateBeforeReset = {
   uiCustomizationState: null,
   drawInTitlebar: null,
+  currentTheme: null,
   gUIStateBeforeReset: null,
 };
 
 XPCOMUtils.defineLazyGetter(this, "log", () => {
   let scope = {};
   Cu.import("resource://gre/modules/Console.jsm", scope);
   let debug;
   try {
@@ -2523,22 +2526,24 @@ var CustomizableUIInternal = {
 
     gResetting = false;
   },
 
   _resetUIState: function() {
     try {
       gUIStateBeforeReset.drawInTitlebar = Services.prefs.getBoolPref(kPrefDrawInTitlebar);
       gUIStateBeforeReset.uiCustomizationState = Services.prefs.getCharPref(kPrefCustomizationState);
+      gUIStateBeforeReset.currentTheme = LightweightThemeManager.currentTheme;
     } catch(e) { }
 
     this._resetExtraToolbars();
 
     Services.prefs.clearUserPref(kPrefCustomizationState);
     Services.prefs.clearUserPref(kPrefDrawInTitlebar);
+    LightweightThemeManager.currentTheme = null;
     log.debug("State reset");
 
     // Reset placements to make restoring default placements possible.
     gPlacements = new Map();
     gDirtyAreaCache = new Set();
     gSeenWidgets = new Set();
     // Clear the saved state to ensure that defaults will be used.
     gSavedState = null;
@@ -2597,23 +2602,25 @@ var CustomizableUIInternal = {
     if (gUIStateBeforeReset.uiCustomizationState == null ||
         gUIStateBeforeReset.drawInTitlebar == null) {
       return;
     }
     gUndoResetting = true;
 
     let uiCustomizationState = gUIStateBeforeReset.uiCustomizationState;
     let drawInTitlebar = gUIStateBeforeReset.drawInTitlebar;
+    let currentTheme = gUIStateBeforeReset.currentTheme;
 
     // Need to clear the previous state before setting the prefs
     // because pref observers may check if there is a previous UI state.
     this._clearPreviousUIState();
 
     Services.prefs.setCharPref(kPrefCustomizationState, uiCustomizationState);
     Services.prefs.setBoolPref(kPrefDrawInTitlebar, drawInTitlebar);
+    LightweightThemeManager.currentTheme = currentTheme;
     this.loadSavedState();
     // If the user just customizes toolbar/titlebar visibility, gSavedState will be null
     // and we don't need to do anything else here:
     if (gSavedState) {
       for (let areaId of Object.keys(gSavedState.placements)) {
         let placements = gSavedState.placements[areaId];
         gPlacements.set(areaId, placements);
       }
@@ -2782,16 +2789,21 @@ var CustomizableUIInternal = {
       }
     }
 
     if (Services.prefs.prefHasUserValue(kPrefDrawInTitlebar)) {
       log.debug(kPrefDrawInTitlebar + " pref is non-default");
       return false;
     }
 
+    if(LightweightThemeManager.currentTheme) {
+      log.debug(LightweightThemeManager.currentTheme + " theme is non-default");
+      return false;
+    }
+
     return true;
   },
 
   setToolbarVisibility: function(aToolbarId, aIsVisible) {
     // We only persist the attribute the first time.
     let isFirstChangedToolbar = true;
     for (let window of CustomizableUI.windows) {
       let toolbar = window.document.getElementById(aToolbarId);
@@ -3486,17 +3498,18 @@ this.CustomizableUI = {
   /**
    * Can the last Restore Defaults operation be undone.
    *
    * @return A boolean stating whether an undo of the
    *         Restore Defaults can be performed.
    */
   get canUndoReset() {
     return gUIStateBeforeReset.uiCustomizationState != null ||
-           gUIStateBeforeReset.drawInTitlebar != null;
+           gUIStateBeforeReset.drawInTitlebar != null ||
+           gUIStateBeforeReset.currentTheme != null;
   },
 
   /**
    * Get the placement of a widget. This is by far the best way to obtain
    * information about what the state of your widget is. The internals of
    * this call are cheap (no DOM necessary) and you will know where the user
    * has put your widget.
    *

--- a/browser/components/customizableui/CustomizeMode.jsm
+++ b/browser/components/customizableui/CustomizeMode.jsm
@@ -1170,16 +1170,18 @@ CustomizeMode.prototype = {
     btn.disabled = true;
     return Task.spawn(function*() {
       this._removePanelCustomizationPlaceholders();
       yield this.depopulatePalette();
       yield this._unwrapToolbarItems();
 
       CustomizableUI.reset();
 
+      this.swatchForTheme(this.document);
+
       yield this._wrapToolbarItems();
       this.populatePalette();
 
       this.persistCurrentSets(true);
 
       this._updateResetButton();
       this._updateUndoResetButton();
       this._updateEmptyPaletteNotice();
@@ -1196,16 +1198,18 @@ CustomizeMode.prototype = {
 
     return Task.spawn(function*() {
       this._removePanelCustomizationPlaceholders();
       yield this.depopulatePalette();
       yield this._unwrapToolbarItems();
 
       CustomizableUI.undoReset();
 
+      this.swatchForTheme(this.document);
+
       yield this._wrapToolbarItems();
       this.populatePalette();
 
       this.persistCurrentSets(true);
 
       this._updateResetButton();
       this._updateUndoResetButton();
       this._updateEmptyPaletteNotice();
@@ -1453,16 +1457,19 @@ CustomizeMode.prototype = {
     this.swatchForTheme(doc);
     for (let element of [footer, recommendedLabel]) {
       while (element.previousSibling &&
              element.previousSibling.localName == "toolbarbutton") {
         element.previousSibling.remove();
       }
     }
     aEvent.target.removeAttribute("height");
+
+    if(LightweightThemeManager.currentTheme)
+      this._onUIChange();
   },
 
   _onUIChange: function() {
     this._changed = true;
     if (!this.resetting) {
       this._updateResetButton();
       this._updateUndoResetButton();
       this._updateEmptyPaletteNotice();

--- a/browser/components/customizableui/test/browser_1007336_lwthemes_in_customize_mode.js
+++ b/browser/components/customizableui/test/browser_1007336_lwthemes_in_customize_mode.js
@@ -47,16 +47,32 @@ add_task(function* () {
      "The second theme in the 'My Themes' section should be the newly installed theme: " +
      "Installed theme id: " + installedThemeId + "; First theme ID: " + firstLWThemeId);
   is(header.nextSibling.nextSibling.nextSibling, recommendedHeader,
      "There should be two themes in the 'My Themes' section");
 
   let defaultTheme = header.nextSibling;
   defaultTheme.doCommand();
   is(Services.prefs.getCharPref("lightweightThemes.selectedThemeID"), "", "No lwtheme should be selected");
+
+  // ensure current theme isn't set to "Default"
+  popupShownPromise = popupShown(popup);
+  EventUtils.synthesizeMouseAtCenter(themesButton, {});
+  info("Clicked on themes button a second time");
+  yield popupShownPromise;
+
+  firstLWTheme = recommendedHeader.nextSibling;
+  themeChangedPromise = promiseObserverNotified("lightweight-theme-changed");
+  firstLWTheme.doCommand();
+  info("Clicked on first theme again");
+  yield themeChangedPromise;
+
+  // check that "Restore Defaults" button resets theme
+  yield gCustomizeMode.reset();
+  is(LightweightThemeManager.currentTheme, null, "Current theme reset to default");
 });
 
 add_task(function* asyncCleanup() {
   yield endCustomizing();
 
   Services.prefs.clearUserPref("lightweightThemes.usedThemes");
   Services.prefs.clearUserPref("lightweightThemes.recommendedThemes");
 });

--- a/browser/components/customizableui/test/browser_970511_undo_restore_default.js
+++ b/browser/components/customizableui/test/browser_970511_undo_restore_default.js
@@ -1,33 +1,52 @@
 /* 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";
 
 requestLongerTimeout(2);
 
-// Restoring default should show an "undo" option which undoes the restoring operation.
+// Restoring default should reset theme and show an "undo" option which undoes the restoring operation.
 add_task(function*() {
   let homeButtonId = "home-button";
   CustomizableUI.removeWidgetFromArea(homeButtonId);
   yield startCustomizing();
   ok(!CustomizableUI.inDefaultState, "Not in default state to begin with");
   is(CustomizableUI.getPlacementOfWidget(homeButtonId), null, "Home button is in palette");
   let undoResetButton = document.getElementById("customization-undo-reset-button");
   is(undoResetButton.hidden, true, "The undo button is hidden before reset");
 
+  let themesButton = document.getElementById("customization-lwtheme-button");
+  let popup = document.getElementById("customization-lwtheme-menu");
+  let popupShownPromise = popupShown(popup);
+  EventUtils.synthesizeMouseAtCenter(themesButton, {});
+  info("Clicked on themes button");
+  yield popupShownPromise;
+
+  let recommendedHeader = document.getElementById("customization-lwtheme-menu-recommended");
+  let firstLWTheme = recommendedHeader.nextSibling;
+  let firstLWThemeId = firstLWTheme.theme.id;
+  let themeChangedPromise = promiseObserverNotified("lightweight-theme-changed");
+  firstLWTheme.doCommand();
+  info("Clicked on first theme");
+  yield themeChangedPromise;
+
+  is(LightweightThemeManager.currentTheme.id, firstLWThemeId, "Theme changed to first option");
+
   yield gCustomizeMode.reset();
 
   ok(CustomizableUI.inDefaultState, "In default state after reset");
   is(undoResetButton.hidden, false, "The undo button is visible after reset");
+  is(LightweightThemeManager.currentTheme, null, "Theme reset to default");
 
   yield gCustomizeMode.undoReset()
 
+  is(LightweightThemeManager.currentTheme.id, firstLWThemeId, "Theme has been reset from default to original choice");
   ok(!CustomizableUI.inDefaultState, "Not in default state after undo-reset");
   is(undoResetButton.hidden, true, "The undo button is hidden after clicking on the undo button");
   is(CustomizableUI.getPlacementOfWidget(homeButtonId), null, "Home button is in palette");
 
   yield gCustomizeMode.reset();
 });
 
 // Performing an action after a reset will hide the reset button.