diff --git a/code/controllers/GoogleSitemapController.php b/code/controllers/GoogleSitemapController.php
index c84c860..db06e2e 100644
--- a/code/controllers/GoogleSitemapController.php
+++ b/code/controllers/GoogleSitemapController.php
@@ -60,7 +60,7 @@ class GoogleSitemapController extends Controller
         $class = $this->unsanitiseClassName($this->request->param('ID'));
         $page = $this->request->param('OtherID');
 
-        if (GoogleSitemap::enabled() && $class && $page) {
+        if (GoogleSitemap::enabled() && $class && $page && ($class=='SiteTree' || GoogleSitemap::is_registered($class))) {
             Config::inst()->update('SSViewer', 'set_source_file_comments', false);
             
             $this->getResponse()->addHeader('Content-Type', 'application/xml; charset="utf-8"');