diff --git a/public/src/client/topic.js b/public/src/client/topic.js
index 0a0d857663..57d276d986 100644
--- a/public/src/client/topic.js
+++ b/public/src/client/topic.js
@@ -23,7 +23,7 @@ define('forum/topic', [
 			Topic.replaceURLTimeout = 0;
 		}
 
-		if (data.url && !data.url.startsWith('topic/')) {
+		if (!String(data.url).startsWith('topic/')) {
 			navigator.disable();
 			components.get('navbar/title').find('span').text('').hide();
 			app.removeAlert('bookmark');