diff --git a/docs/error-handling.md b/docs/error-handling.md
index 1a902cc..f21bf0c 100644
--- a/docs/error-handling.md
+++ b/docs/error-handling.md
@@ -283,8 +283,8 @@ Only `opened`, `edited`, `reopened` and `synchronize` pull_request events
 are queued. The bot's own body update comes back as an `edited` event and
 is recognised by its sender. A PR already queued or running is not queued
 twice. Unverified requests in production are logged at `warn` as
-`Unverified request: <method> <url> from <address>` and fall through to
-Express's 404.
+`Unverified request: <method> <url> from <address>` and answered with a
+401, so a mismatched secret shows up as such in GitHub's delivery log.
 
 **Config tester** (`POST /config`). Validation errors (bad repo name,
 invalid JSON, schema violations, a repo with no PRs) are answered with a
diff --git a/lib/app.js b/lib/app.js
index 8df1556..3213de9 100644
--- a/lib/app.js
+++ b/lib/app.js
@@ -22,7 +22,7 @@ module.exports = function createApp(controller, config, log) {
     // Everything else is acknowledged and logged as ignored, with the same
     // status and reason fields as a processed job, so the log says what
     // arrived and what became of it.
-    app.post('/github-hook', function (req, res, next) {
+    app.post('/github-hook', function (req, res) {
         if (config.nodeEnv != 'production' || (typeof req.isXHubValid === 'function' && req.isXHubValid())) {
             res.send(new Date().toISOString());
             const payload = req.body;
@@ -63,8 +63,8 @@ module.exports = function createApp(controller, config, log) {
             const ip = req.headers["x-forwarded-for"] || req.socket.remoteAddress;
             log.warn({ method: req.method, url: req.originalUrl, ip },
                 `Unverified request: ${req.method} ${req.originalUrl} from ${ip}`);
+            res.sendStatus(401);
         }
-        next();
     });
 
     // Deployment health check. Clever Cloud calls the path named in
@@ -82,7 +82,7 @@ module.exports = function createApp(controller, config, log) {
         });
     });
 
-    app.post('/config', bodyParser.urlencoded({ extended: false }), async function (req, res, next) {
+    app.post('/config', bodyParser.urlencoded({ extended: false }), async function (req, res) {
         try {
             let params = req.body;
             let url;
@@ -95,8 +95,6 @@ module.exports = function createApp(controller, config, log) {
         } catch (err) {
             res.status(400).send({ error: err.message });
             log.error({ err, url: req.originalUrl }, `${req.originalUrl}: request failed`);
-        } finally {
-            next();
         }
     });
 
diff --git a/test/server.js b/test/server.js
index 7662094..ebf3912 100644
--- a/test/server.js
+++ b/test/server.js
@@ -178,7 +178,7 @@ suite('Server signature verification', () => {
             .set('Content-Type', 'application/json')
             .set('X-Hub-Signature', sign('wrong-secret', BODY))
             .send(BODY)
-            .expect(404)
+            .expect(401)
             .end(done);
     });
 
@@ -189,7 +189,7 @@ suite('Server signature verification', () => {
             .post('/github-hook')
             .set('Content-Type', 'application/json')
             .send(BODY)
-            .expect(404)
+            .expect(401)
             .end(done);
     });
 });