diff --git a/src/activitypub/helpers.js b/src/activitypub/helpers.js
index 3b6e7549aa..d06a058201 100644
--- a/src/activitypub/helpers.js
+++ b/src/activitypub/helpers.js
@@ -483,14 +483,15 @@ Helpers.generateCollection = async ({ set, method, count, page, perPage, url })
 		paginate = false;
 	}
 
-	page = parseInt(page, 10) || undefined;
+	page = parseInt(page, 10) || 1;
+	page = Math.max(1, Math.min(page, pageCount));
 	if (page) {
 		const invalidPagination = page < 1 || page > pageCount;
 		if (invalidPagination) {
 			throw new Error('[[error:invalid-data]]');
 		}
 
-		const start = Math.max(0, ((page - 1) * perPage) - 1);
+		const start = Math.max(0, (page - 1) * perPage);
 		const stop = Math.max(0, start + perPage - 1);
 		items = await method.call(null, start, stop);
 	}
diff --git a/src/controllers/activitypub/actors.js b/src/controllers/activitypub/actors.js
index dddd402f2d..6745d42290 100644
--- a/src/controllers/activitypub/actors.js
+++ b/src/controllers/activitypub/actors.js
@@ -150,10 +150,10 @@ Actors.topic = async function (req, res, next) {
 		} catch (e) {
 			return next(); // invalid page; 404
 		}
-		pids.push(mainPid);
-		pids = pids.map(pid => (utils.isNumber(pid) ? `${nconf.get('url')}/post/${pid}` : pid));
 
 		// Generate digest for ETag
+		pids.push(mainPid);
+		pids = pids.map(pid => (utils.isNumber(pid) ? `${nconf.get('url')}/post/${pid}` : pid));
 		const digest = activitypub.helpers.generateDigest(new Set(pids));
 		const ifNoneMatch = (req.get('If-None-Match') || '').split(',').map((tag) => {
 			tag = tag.trim();
@@ -169,11 +169,11 @@ Actors.topic = async function (req, res, next) {
 		res.set('ETag', digest);
 
 		// Add OP to collection on first (or only) page
+		collection.totalItems += 1; // account for mainPid
 		if (page || collection.totalItems < perPage) {
 			collection.orderedItems = collection.orderedItems || [];
 			if (!page || page === 1) {
 				collection.orderedItems.unshift(mainPid);
-				collection.totalItems += 1;
 			}
 		}