diff --git a/src/activitypub/inbox.js b/src/activitypub/inbox.js
index e224ab1599..770ae1a4ca 100644
--- a/src/activitypub/inbox.js
+++ b/src/activitypub/inbox.js
@@ -25,7 +25,7 @@ inbox.create = async (req) => {
 		throw new Error('[[error:activitypub.not-implemented]]');
 	}
 
-	const { tid, count } = await activitypub.notes.assertTopic(0, object.id);
+	const { tid, count } = await activitypub.notes.assert(0, object.id);
 	winston.verbose(`[activitypub/inbox] Parsing ${count} notes into topic ${tid}`);
 };
 
@@ -47,7 +47,7 @@ inbox.update = async (req) => {
 				if (exists) {
 					await posts.edit(postData);
 				} else {
-					await activitypub.notes.assertTopic(0, object.id);
+					await activitypub.notes.assert(0, object.id);
 				}
 			} catch (e) {
 				activitypub.send('uid', 0, actor, {
@@ -129,7 +129,7 @@ inbox.announce = async (req) => {
 			return;
 		}
 
-		({ tid } = await activitypub.notes.assertTopic(0, pid));
+		({ tid } = await activitypub.notes.assert(0, pid, object));
 		if (!tid) {
 			return;
 		}
diff --git a/src/activitypub/notes.js b/src/activitypub/notes.js
index 2d3cb9a01d..0fb9bcf040 100644
--- a/src/activitypub/notes.js
+++ b/src/activitypub/notes.js
@@ -2,6 +2,7 @@
 
 const winston = require('winston');
 const crypto = require('crypto');
+const nconf = require('nconf');
 
 const db = require('../database');
 const meta = require('../meta');
@@ -15,15 +16,15 @@ const utils = require('../utils');
 const activitypub = module.parent.exports;
 const Notes = module.exports;
 
-Notes.assert = async (uid, id) => {
+Notes.assert = async (uid, id, object) => {
 	/**
-	 * Given the id of any post, traverses up to cache the entire threaded context
+	 * Given the id (or optional AS object) of any post, traverses up to cache the entire threaded context
 	 *
 	 * Unfortunately, due to limitations and fragmentation of the existing ActivityPub landscape,
 	 * retrieving the entire reply tree is not possible at this time.
 	 */
 
-	const chain = Array.from(await Notes.getParentChain(uid, id));
+	const chain = Array.from(await Notes.getParentChain(uid, object || id));
 	if (!chain.length) {
 		return null;
 	}
@@ -124,6 +125,19 @@ Notes.assert = async (uid, id) => {
 			Notes.updateLocalRecipients(post.pid, { to, cc }),
 			Notes.saveAttachments(post.pid, attachment),
 		]);
+
+		// Category announce
+		if (id === post.id) {
+			// eslint-disable-next-line no-await-in-loop
+			const followers = await activitypub.notes.getCategoryFollowers(cid);
+			// eslint-disable-next-line no-await-in-loop
+			await activitypub.send('cid', cid, followers, {
+				type: 'Announce',
+				to: [`${nconf.get('url')}/category/${cid}/followers`],
+				cc: [activitypub._constants.publicAddress],
+				object,
+			});
+		}
 	}
 
 	await Notes.syncUserInboxes(tid);
@@ -213,9 +227,9 @@ Notes.getParentChain = async (uid, input) => {
 				}
 			}
 		} else {
-			let object;
+			let object = !activitypub.helpers.isUri(input) && input.id === id ? input : undefined;
 			try {
-				object = await activitypub.get('uid', uid, id);
+				object = object || await activitypub.get('uid', uid, id);
 
 				// Handle incorrect id passed in
 				if (id !== object.id) {
diff --git a/src/api/activitypub.js b/src/api/activitypub.js
index bd8d700908..0d21d6e0b1 100644
--- a/src/api/activitypub.js
+++ b/src/api/activitypub.js
@@ -123,7 +123,9 @@ activitypubApi.create.post = enabledCheck(async (caller, { pid }) => {
 	};
 
 	await activitypub.send('uid', caller.uid, Array.from(targets), payloads.create);
-	await activitypub.send('cid', cid, followers, payloads.announce);
+	if (followers.length) {
+		await activitypub.send('cid', cid, followers, payloads.announce);
+	}
 });
 
 activitypubApi.update = {};