diff --git a/src/activitypub/inbox.js b/src/activitypub/inbox.js
index bafed33183..4308d1c9de 100644
--- a/src/activitypub/inbox.js
+++ b/src/activitypub/inbox.js
@@ -93,10 +93,12 @@ inbox.announce = async (req) => {
 		tid = await posts.getPostField(id, 'tid');
 	} else {
 		pid = object;
-		([pid, tid] = await Promise.all([
-			activitypub.notes.resolveId(0, pid),
-			activitypub.notes.assertTopic(0, pid),
-		]));
+		pid = await activitypub.resolveId(0, pid); // in case wrong id is passed-in; unlikely, but still.
+		if (!pid) {
+			return;
+		}
+
+		tid = await activitypub.notes.assertTopic(0, pid);
 		if (!tid) {
 			return;
 		}
diff --git a/src/activitypub/index.js b/src/activitypub/index.js
index 6f787b7b4f..4f2235100a 100644
--- a/src/activitypub/index.js
+++ b/src/activitypub/index.js
@@ -24,6 +24,23 @@ ActivityPub.mocks = require('./mocks');
 ActivityPub.notes = require('./notes');
 ActivityPub.actors = require('./actors');
 
+ActivityPub.resolveId = async (uid, id) => {
+	try {
+		const query = new URL(id);
+		({ id } = await ActivityPub.get('uid', uid, id));
+		const response = new URL(id);
+
+		if (query.host !== response.host) {
+			winston.warn(`[activitypub/resolveId] id resolution domain mismatch: ${query.href} != ${response.href}`);
+			return null;
+		}
+
+		return id;
+	} catch (e) {
+		return null;
+	}
+};
+
 ActivityPub.resolveInboxes = async (ids) => {
 	const inboxes = new Set();
 
diff --git a/src/activitypub/notes.js b/src/activitypub/notes.js
index 068fd8cb51..795c807d26 100644
--- a/src/activitypub/notes.js
+++ b/src/activitypub/notes.js
@@ -14,11 +14,6 @@ const slugify = require('../slugify');
 const activitypub = module.parent.exports;
 const Notes = module.exports;
 
-Notes.resolveId = async (uid, id) => {
-	({ id } = await activitypub.get('uid', uid, id));
-	return id;
-};
-
 // todo: when asserted, notes aren't added to a global sorted set
 // also, db.exists call is probably expensive
 Notes.assert = async (uid, input, options = {}) => {
@@ -28,8 +23,13 @@ Notes.assert = async (uid, input, options = {}) => {
 	await Promise.all(input.map(async (item) => {
 		let id = activitypub.helpers.isUri(item) ? item : item.pid;
 		if (activitypub.helpers.isUri(id)) {
-			id = await Notes.resolveId(uid, id);
+			id = await activitypub.resolveId(uid, id);
+			if (!id) {
+				winston.warn(`[activitypub/notes.assert] Not asserting ${id}`);
+				return;
+			}
 		}
+
 		const key = `post:${id}`;
 		const exists = await db.exists(key);
 		winston.verbose(`[activitypub/notes.assert] Asserting note id ${id}`);
diff --git a/test/activitypub.js b/test/activitypub.js
index d002bca19d..e1c052e377 100644
--- a/test/activitypub.js
+++ b/test/activitypub.js
@@ -88,6 +88,40 @@ describe('ActivityPub integration', () => {
 
 		});
 
+		describe.only('.resolveId()', () => {
+			let url;
+			let resolved;
+
+			before(() => {
+				url = 'https://example.org/topic/foobar';
+				resolved = 'https://example.org/tid/1234';
+				activitypub._cache.set(`0;${url}`, {
+					id: resolved,
+				});
+			});
+
+			it('should return the resolved id when queried', async () => {
+				const id = await activitypub.resolveId(0, url);
+				assert.strictEqual(id, resolved);
+			});
+
+			it('should return null when the query fails', async () => {
+				const id = await activitypub.resolveId(0, 'https://example.org/sdlknsdfnsd');
+				assert.strictEqual(id, null);
+			});
+
+			it('should return null when the resolved host does not match the queried host', async () => {
+				const url = 'https://example.com/topic/foobar'; // .com attempting to overwrite .org data
+				const resolved = 'https://example.org/tid/1234'; // .org
+				activitypub._cache.set(`0;${url}`, {
+					id: resolved,
+				});
+
+				const id = await activitypub.resolveId(0, url);
+				assert.strictEqual(id, null);
+			});
+		});
+
 		describe('.resolveLocalId()', () => {
 			let uid;
 			let slug;