diff --git a/src/controllers/activitypub/topics.js b/src/controllers/activitypub/topics.js
index 69c682d2cb..2ea0132d0c 100644
--- a/src/controllers/activitypub/topics.js
+++ b/src/controllers/activitypub/topics.js
@@ -46,13 +46,11 @@ controller.list = async function (req, res) {
 	]);
 	const sort = validSorts.includes(req.query.sort) ? req.query.sort : userSettings.categoryTopicSort;
 
-	const sets = [sortToSet[sort], `uid:${req.uid}:inbox`];
-	const tids = await db.getSortedSetRevIntersect({
-		sets,
-		start,
-		stop,
-		weights: sets.map((s, index) => (index ? 0 : 1)),
-	});
+	let tids = await db.getSortedSetRevRange(sortToSet[sort], 0, 499);
+	const isMembers = await db.isSortedSetMembers(`uid:${req.uid}:inbox`, tids);
+	tids = tids.filter((tid, idx) => isMembers[idx]);
+	const count = tids.length;
+	tids = tids.slice(start, stop);
 
 	const targetUid = await user.getUidByUserslug(req.query.author);
 
@@ -71,7 +69,7 @@ controller.list = async function (req, res) {
 	data.name = '[[activitypub:world.name]]';
 	delete data.children;
 
-	data.topicCount = await db.sortedSetIntersectCard(sets);
+	data.topicCount = count;
 	data.topics = await topics.getTopicsByTids(tids, { uid: req.uid });
 	topics.calculateTopicIndices(data.topics, start);
 
diff --git a/src/upgrades/4.0.0/prune_user_inboxes.js b/src/upgrades/4.0.0/prune_user_inboxes.js
new file mode 100644
index 0000000000..7ea27d322e
--- /dev/null
+++ b/src/upgrades/4.0.0/prune_user_inboxes.js
@@ -0,0 +1,29 @@
+'use strict';
+
+const db = require('../../database');
+const batch = require('../../batch');
+const topics = require('../../topics');
+
+module.exports = {
+	name: 'Prune deleted topics out of user inboxes',
+	timestamp: Date.UTC(2024, 6, 12),
+	method: async function () {
+		const { progress } = this;
+
+		await batch.processSortedSet('users:joindate', async (uids) => {
+			const exists = await db.exists(uids.map(uid => `uid:${uid}:inbox`));
+			const count = uids.length;
+			uids = uids.filter((uid, idx) => exists[idx]);
+
+			await Promise.all(uids.map(async (uid) => {
+				const key = `uid:${uid}:inbox`;
+				const tids = await db.getSortedSetMembers(key);
+				const exists = await topics.exists(tids);
+				const toRemove = tids.filter((tid, idx) => !exists[idx]);
+				await db.sortedSetRemove(key, toRemove);
+			}));
+
+			progress.incr(count);
+		}, { progress });
+	},
+};