diff --git a/src/activitypub/feps.js b/src/activitypub/feps.js
index d22731fd79..3611ad805a 100644
--- a/src/activitypub/feps.js
+++ b/src/activitypub/feps.js
@@ -3,6 +3,7 @@
 const nconf = require('nconf');
 
 const posts = require('../posts');
+const utils = require('../utils');
 
 const activitypub = module.parent.exports;
 const Feps = module.exports;
@@ -69,7 +70,7 @@ Feps.announceObject = async function announceObject(id) {
 	}
 
 	const author = await posts.getPostField(id, 'uid');
-	if (!author.startsWith(nconf.get('url'))) {
+	if (!utils.isNumber(author) && !author.startsWith(nconf.get('url'))) {
 		followers.unshift(author);
 	}
 
diff --git a/test/activitypub/feps.js b/test/activitypub/feps.js
new file mode 100644
index 0000000000..e8a826e4e2
--- /dev/null
+++ b/test/activitypub/feps.js
@@ -0,0 +1,68 @@
+'use strict';
+
+const assert = require('assert');
+const nconf = require('nconf');
+
+const db = require('../mocks/databasemock');
+const activitypub = require('../../src/activitypub');
+const utils = require('../../src/utils');
+const meta = require('../../src/meta');
+const install = require('../../src/install');
+const user = require('../../src/user');
+const groups = require('../../src/groups');
+const categories = require('../../src/categories');
+const topics = require('../../src/topics');
+const api = require('../../src/api');
+
+const helpers = require('./helpers');
+
+describe('FEPs', () => {
+	before(async () => {
+		meta.config.activitypubEnabled = 1;
+		await install.giveWorldPrivileges();
+	});
+
+	describe('1b12', () => {
+		describe('announceObject()', () => {
+			let cid;
+			let uid;
+			let adminUid;
+
+			before(async () => {
+				const name = utils.generateUUID();
+				const description = utils.generateUUID();
+				({ cid } = await categories.create({ name, description }));
+
+				adminUid = await user.create({ username: utils.generateUUID() });
+				await groups.join('administrators', adminUid);
+				uid = await user.create({ username: utils.generateUUID() });
+
+				const { id: followerId, actor } = helpers.mocks.actor();
+				activitypub._cache.set(`0;${followerId}`, actor);
+				user.setCategoryWatchState(followerId, [cid], categories.watchStates.tracking);
+
+				activitypub._sent.clear();
+			});
+
+			it('should be called when a topic is moved from uncategorized to another category', async () => {
+				const { topicData } = await topics.post({
+					uid,
+					cid: -1,
+					title: utils.generateUUID(),
+					content: utils.generateUUID(),
+				});
+
+				assert(topicData);
+
+				await api.topics.move({ uid: adminUid }, {
+					tid: topicData.tid,
+					cid,
+				});
+
+				setTimeout(() => {
+					assert.strictEqual(activitypub._sent.size, 1);
+				}, 250);
+			});
+		});
+	});
+});
diff --git a/test/activitypub/helpers.js b/test/activitypub/helpers.js
index 23fc29be14..9df1222144 100644
--- a/test/activitypub/helpers.js
+++ b/test/activitypub/helpers.js
@@ -1,12 +1,42 @@
 'use strict';
 
-const utils = require('../../src/utils');
 const activitypub = require('../../src/activitypub');
+const utils = require('../../src/utils');
+const slugify = require('../../src/slugify');
 
 const Helpers = module.exports;
 
 Helpers.mocks = {};
 
+Helpers.mocks.actor = () => {
+	const baseUrl = 'https://example.org';
+	const uuid = utils.generateUUID();
+	const id = `${baseUrl}/${uuid}`;
+
+	const actor = {
+		'@context': [
+			'https://www.w3.org/ns/activitystreams',
+			'https://w3id.org/security/v1',
+		],
+		id: `${id}`,
+		url: `${id}`,
+		inbox: `${id}/inbox`,
+		outbox: `${id}/outbox`,
+
+		type: 'Person',
+		name: slugify(uuid),
+		preferredUsername: uuid,
+
+		publicKey: {
+			id: `${id}#key`,
+			owner: `${id}`,
+			publicKeyPem: 'todo',
+		},
+	};
+
+	return { id, actor };
+};
+
 Helpers.mocks.note = (override = {}) => {
 	const baseUrl = 'https://example.org';
 	const uuid = utils.generateUUID();