diff --git a/src/posts/summary.js b/src/posts/summary.js
index e3e948c292..32651b67c1 100644
--- a/src/posts/summary.js
+++ b/src/posts/summary.js
@@ -121,7 +121,7 @@ module.exports = function(Posts) {
 
 			var cids = topics.map(function(topic) {
 				if (topic) {
-					topic.title = validator.escape(topic.title);
+					topic.title = validator.escape(String(topic.title));
 					topic.deleted = parseInt(topic.deleted, 10) === 1;
 				}
 				return topic && topic.cid;