diff --git a/lib/request.js b/lib/request.js
index 134f0895..d71adc6c 100644
--- a/lib/request.js
+++ b/lib/request.js
@@ -6,7 +6,6 @@ const {Agent: HttpsAgent} = require('https')
 const roundRobin = require('@derhuerst/round-robin-scheduler')
 const {randomBytes} = require('crypto')
 const createHash = require('create-hash')
-const pick = require('lodash/pick')
 const {stringify} = require('qs')
 const {Request, fetch} = require('cross-fetch')
 const {parse: parseContentType} = require('content-type')
@@ -70,14 +69,13 @@ const request = async (ctx, userAgent, reqData) => {
 		// todo: is it `eng` actually?
 		// RSAG has `deu` instead of `de`
 		lang: opt.language || profile.defaultLanguage || 'en',
-		svcReqL: [reqData]
+		svcReqL: [reqData],
+
+		client: profile.client, // client identification
+		ext: profile.ext, // ?
+		ver: profile.ver, // HAFAS protocol version
+		auth: profile.auth, // static authentication
 	})
-	Object.assign(rawReqBody, pick(profile, [
-		'client', // client identification
-		'ext', // ?
-		'ver', // HAFAS protocol version
-		'auth', // static authentication
-	]))
 
 	const req = profile.transformReq(ctx, {
 		agent: getAgent(),
diff --git a/test/lib/request.js b/test/lib/request.js
new file mode 100644
index 00000000..125a20f0
--- /dev/null
+++ b/test/lib/request.js
@@ -0,0 +1,93 @@
+'use strict'
+
+const tap = require('tap')
+const forEach = require('lodash/forEach')
+const request = require('../../lib/request')
+const formatTripReq = require('../../format/trip-req')
+
+const USER_AGENT = 'public-transport/hafas-client:test'
+
+const freeze = (val) => {
+	if (
+		'object' === typeof val
+		&& val !== null
+		&& !Array.isArray(val)
+	) Object.freeze(val)
+}
+const ctx = {
+	// random but unique
+	opt: {
+		language: 'ga',
+	},
+	profile: {
+		endpoint: 'https://does.not.exist',
+		client: {
+			type: 'FOO',
+			id: 'BAR',
+			name: 'baZ',
+		},
+		auth: {
+			type: 'AID',
+			aid: 'some-auth-token',
+		},
+		ver: '1.23.4',
+
+		timezone: 'Europe/Amsterdam',
+		locale: 'de-LU',
+		defaultLanguage: 'fr',
+
+		transformReq: (_, req) => req,
+	},
+}
+forEach(ctx, freeze)
+
+tap.test('lib/request calls profile.transformReqBody & profile.transformReq properly', async (t) => {
+	const customTransformReqBody = (ctx, reqBody) => {
+		const p = 'transformReqBody call: '
+		t.same(ctx, customCtx, 'ctx should be the passed-in ctx')
+
+		t.ok(reqBody, 'reqBody')
+		t.equal(reqBody.client, ctx.profile.client, p + 'reqBody.client')
+		t.equal(reqBody.ext, ctx.profile.ext, p + 'reqBody.ext')
+		t.equal(reqBody.var, ctx.profile.var, p + 'reqBody.var')
+		t.equal(reqBody.auth, ctx.profile.auth, p + 'reqBody.auth')
+		t.equal(reqBody.lang, ctx.opt.language, p + 'reqBody.lang')
+
+		// We test if lib/request.js handles returning a new object.
+		return {
+			...reqBody,
+		}
+	}
+
+	const customTransformReq = (ctx, req) => {
+		const p = 'transformReq call: '
+		t.same(ctx, customCtx, p + 'ctx should be the passed-in ctx')
+
+		t.equal(typeof req.body, 'string', p + 'req.body')
+		t.ok(req.body, p + 'req.body')
+
+		// We test if lib/request.js handles returning a new object.
+		return {
+			...req,
+			// From node-fetch, used by isomorphic-fetch:
+			// > req/res timeout in ms, it resets on redirect. 0 to disable (OS limit applies). Signal is recommended instead.
+			timeout: 100,
+		}
+	}
+
+	const customCtx = {
+		...ctx,
+		profile: {
+			...ctx.profile,
+			transformReqBody: customTransformReqBody,
+			transformReq: customTransformReq,
+		},
+	}
+	const tripReq = formatTripReq(customCtx, 'unknown-trip-id')
+
+	// todo: set 1s timeout
+	await t.rejects(async () => {
+		await request(customCtx, USER_AGENT, tripReq)
+	})
+	t.end()
+})