diff --git a/server/lib/matrix-utils/ensure-room-joined.js b/server/lib/matrix-utils/ensure-room-joined.js
index aa7af3a..09826f4 100644
--- a/server/lib/matrix-utils/ensure-room-joined.js
+++ b/server/lib/matrix-utils/ensure-room-joined.js
@@ -3,14 +3,19 @@
 const assert = require('assert');
 const urlJoin = require('url-join');
 
+const StatusError = require('../errors/status-error');
 const { fetchEndpointAsJson } = require('../fetch-endpoint');
 const getServerNameFromMatrixRoomIdOrAlias = require('./get-server-name-from-matrix-room-id-or-alias');
+const MatrixPublicArchiveURLCreator = require('matrix-public-archive-shared/lib/url-creator');
 
 const config = require('../config');
-const StatusError = require('../errors/status-error');
+const basePath = config.get('basePath');
+assert(basePath);
 const matrixServerUrl = config.get('matrixServerUrl');
 assert(matrixServerUrl);
 
+const matrixPublicArchiveURLCreator = new MatrixPublicArchiveURLCreator(basePath);
+
 async function ensureRoomJoined(
   accessToken,
   roomIdOrAlias,
@@ -47,7 +52,12 @@ async function ensureRoomJoined(
         reason:
           `Joining room to check history visibility. ` +
           `If your room is public with shared or world readable history visibility, ` +
-          `it will be accessible at archive.matrix.org. ` +
+          `it will be accessible at ${matrixPublicArchiveURLCreator.archiveUrlForRoom(
+            roomIdOrAlias
+            // We don't need to include the `viaServers` option here because the archive
+            // will already be joined to the room from this request itself and we don't
+            // need to make the URL any longer/noisier than it needs to be.
+          )}. ` +
           `See the FAQ for more details: ` +
           `https://github.com/matrix-org/matrix-public-archive/blob/main/docs/faq.md#why-did-the-archive-bot-join-my-room`,
       },