diff --git a/test/trust-proxy.test.js b/test/trust-proxy.test.js
index 4e1ab58573..b97a1fd94e 100644
--- a/test/trust-proxy.test.js
+++ b/test/trust-proxy.test.js
@@ -85,3 +85,35 @@ test('trust proxy chain', (t) => {
     )
   })
 })
+
+test('trust proxy function', (t) => {
+  t.plan(5)
+  const app = fastify({
+    trustProxy: (address) => address === '127.0.0.1'
+  })
+  app.get('/trustproxyfunc', function (req, reply) {
+    t.ok(req.raw.ip, 'ip is defined')
+    t.ok(req.raw.hostname, 'hostname is defined')
+    t.equal(req.raw.ip, '1.1.1.1', 'gets ip from x-forwarder-for')
+    t.equal(req.raw.hostname, 'example.com', 'gets hostname from x-forwarded-host')
+    reply.code(200).send({ip: req.ip, hostname: req.hostname})
+  })
+
+  t.tearDown(app.close.bind(app))
+
+  app.listen(0, (err) => {
+    app.server.unref()
+    t.error(err)
+    sget(
+      {
+        method: 'GET',
+        headers: {
+          'X-Forwarded-For': '1.1.1.1',
+          'X-Forwarded-Host': 'example.com'
+        },
+        url: 'http://localhost:' + app.server.address().port + '/trustproxyfunc'
+      },
+      () => {}
+    )
+  })
+})