diff --git a/app/assets/javascripts/admin/controllers/admin-customize-css-html.js.es6 b/app/assets/javascripts/admin/controllers/admin-customize-css-html.js.es6
index be6834333d9..08e4e3215b4 100644
--- a/app/assets/javascripts/admin/controllers/admin-customize-css-html.js.es6
+++ b/app/assets/javascripts/admin/controllers/admin-customize-css-html.js.es6
@@ -10,6 +10,14 @@ import showModal from 'discourse/lib/show-modal';
 **/
 export default Ember.ArrayController.extend({
 
+  undoPreviewUrl: function() {
+    return Discourse.getURL("/?preview-style=");
+  }.property(),
+
+  defaultStyleUrl: function() {
+    return Discourse.getURL("/?preview-style=default");
+  }.property(),
+
   actions: {
 
     /**
diff --git a/app/assets/javascripts/admin/models/site_customization.js b/app/assets/javascripts/admin/models/site_customization.js
index f7b6346a958..19fcbad266e 100644
--- a/app/assets/javascripts/admin/models/site_customization.js
+++ b/app/assets/javascripts/admin/models/site_customization.js
@@ -44,7 +44,7 @@ Discourse.SiteCustomization = Discourse.Model.extend({
     this.set('originals', originals);
   }.on('init'),
 
-  previewUrl: function() { return "/?preview-style=" + this.get('key'); }.property('key'),
+  previewUrl: function() { return Discourse.getURL("/?preview-style=" + this.get('key')); }.property('key'),
   disableSave: function() { return !this.get('changed') || this.get('saving'); }.property('changed'),
 
   save: function() {
diff --git a/app/assets/javascripts/admin/templates/customize_css_html.hbs b/app/assets/javascripts/admin/templates/customize_css_html.hbs
index e2cc7951a01..f4dce62b091 100644
--- a/app/assets/javascripts/admin/templates/customize_css_html.hbs
+++ b/app/assets/javascripts/admin/templates/customize_css_html.hbs
@@ -65,9 +65,9 @@
           {{#unless selectedItem.changed}}
           <a class='preview-link' {{bind-attr href="selectedItem.previewUrl"}} target='_blank' title="{{i18n 'admin.customize.explain_preview'}}">{{i18n 'admin.customize.preview'}}</a>
           |
-          <a href="/?preview-style=" target='_blank' title="{{i18n 'admin.customize.explain_undo_preview'}}">{{i18n 'admin.customize.undo_preview'}}</a>
+          <a href="{{undoPreviewUrl}}" target='_blank' title="{{i18n 'admin.customize.explain_undo_preview'}}">{{i18n 'admin.customize.undo_preview'}}</a>
           |
-          <a href="/?preview-style=default" target='_blank' title="{{i18n 'admin.customize.explain_rescue_preview'}}">{{i18n 'admin.customize.rescue_preview'}}</a><br>
+          <a href="{{defaultStyleUrl}}" target='_blank' title="{{i18n 'admin.customize.explain_rescue_preview'}}">{{i18n 'admin.customize.rescue_preview'}}</a><br>
           {{/unless}}
         </div>