diff --git a/code/extensions/GoogleSitemapSiteTreeExtension.php b/code/extensions/GoogleSitemapSiteTreeExtension.php
index 839bcaf..7d3d85b 100644
--- a/code/extensions/GoogleSitemapSiteTreeExtension.php
+++ b/code/extensions/GoogleSitemapSiteTreeExtension.php
@@ -62,7 +62,7 @@ class GoogleSitemapSiteTreeExtension extends GoogleSitemapExtension {
 	 */
 	public function canIncludeInGoogleSitemap() {
 		$result = parent::canIncludeInGoogleSitemap();
-		$result = ($this instanceof ErrorPage) ? false : $result;
+		$result = ($this->owner instanceof ErrorPage) ? false : $result;
 
 		return $result;
 	}