diff --git a/src/topics/thumbs.js b/src/topics/thumbs.js
index 9fd62eb0e4..5c6d62b263 100644
--- a/src/topics/thumbs.js
+++ b/src/topics/thumbs.js
@@ -54,7 +54,8 @@ Thumbs.get = async function (tids) {
 	const thumbs = await Promise.all(sets.map(getThumbs));
 
 	// Add attachments to thumb sets
-	const mainPids = await topics.getTopicsFields(tids, ['mainPid']);
+	let mainPids = await topics.getTopicsFields(tids, ['mainPid']);
+	mainPids = mainPids.map(o => o.mainPid);
 	const mainPidAttachments = await posts.attachments.get(mainPids);
 	mainPidAttachments.forEach((attachments, idx) => {
 		attachments = attachments.filter(