diff --git a/p/dbnav/journeys-req.js b/p/dbnav/journeys-req.js
index 4c07bf1f..8cc8631f 100644
--- a/p/dbnav/journeys-req.js
+++ b/p/dbnav/journeys-req.js
@@ -31,7 +31,7 @@ const formatJourneysReq = (ctx, from, to, when, outFrwd, journeysRef) => {
 	from = profile.formatLocation(profile, from, 'from');
 	to = profile.formatLocation(profile, to, 'to');
 	const filters = profile.formatProductsFilter({profile}, opt.products || {}, 'dbnav');
-	const transfers = profile.formatTransfers(opt.transfers) ?? undefined; // `dbnav` does not allow `undefined` here
+	const transfers = profile.formatTransfers(opt.transfers) ?? undefined; // `dbnav` does not allow `null` here
 	// TODO opt.accessibility
 	// TODO routingMode
 	let query = formatBaseJourneysReq(ctx);
diff --git a/readme.md b/readme.md
index 479d0bce..6e7dc98a 100644
--- a/readme.md
+++ b/readme.md
@@ -30,7 +30,8 @@ Depending on the configured profile, db-vendo-client will use multiple different
 | cancelled trips       | not contained in boards | contained with cancelled flag |
 | tickets               | only for `refreshJourney()` | only for `refreshJourney()`, mutually exclusive with polylines |
 | polylines             | only for `trip()` | only for `refreshJourney()/trip()`, mutually exclusive with tickets |
-| trip ids used         | HAFAS trip ids for journeys, RIS trip ids for boards | HAFAS trip ids |
+| trip ids used         | HAFAS trip ids for journeys, RIS trip ids for boards (static on train splits?) | HAFAS trip ids |
+| line.id/fahrtNr used  | unreliable/route id for journeys, actual fahrtNr for boards | unreliable/route id |
 | `stop()`              | ❌ | ✅ |
 | assumed backend API stability | less stable | more stable |
 
diff --git a/test/format/dbnav-journeys-query.js b/test/format/dbnav-journeys-query.js
new file mode 100644
index 00000000..b5fb6342
--- /dev/null
+++ b/test/format/dbnav-journeys-query.js
@@ -0,0 +1,136 @@
+import tap from 'tap';
+
+import {createClient} from '../../index.js';
+import {profile as rawProfile} from '../../p/dbnav/index.js';
+import {data as loyaltyCards} from '../../format/loyalty-cards.js';
+
+const client = createClient(rawProfile, 'public-transport/hafas-client:test');
+const {profile} = client;
+
+const opt = {
+	results: null,
+	via: null,
+	stopovers: false,
+	transfers: null,
+	transferTime: 0,
+	accessibility: 'none',
+	bike: false,
+	walkingSpeed: 'normal',
+	startWithWalking: true,
+	tickets: false,
+	polylines: false,
+	subStops: true,
+	entrances: true,
+	remarks: true,
+	scheduledDays: false,
+	departure: '2023-09-12T08:09:10+02:00',
+	products: {},
+
+	firstClass: false,
+	age: 24,
+	loyaltyCard: {
+		type: loyaltyCards.BAHNCARD,
+		discount: 25,
+	},
+};
+
+const berlinWienQuery0 = Object.freeze(
+	{
+		autonomeReservierung: false,
+		reservierungsKontingenteVorhanden: false,
+		einstiegsTypList: [
+			'STANDARD',
+		],
+		klasse: 'KLASSE_2',
+		reiseHin: {
+			wunsch: {
+				abgangsLocationId: 'A=1@L=8098160@',
+				verkehrsmittel: [
+					'ALL',
+				],
+				zeitWunsch: {
+					reiseDatum: '2024-12-07T23:50:12+01:00',
+					zeitPunktArt: 'ABFAHRT',
+				},
+				viaLocations: undefined,
+				zielLocationId: 'A=1@L=8000284@',
+				maxUmstiege: undefined,
+				minUmstiegsdauer: undefined,
+				fahrradmitnahme: false,
+			},
+		},
+	});
+
+tap.test('formats a journeys() request correctly (DBnav)', (t) => {
+	const _opt = {...opt};
+	delete _opt.loyaltyCard;
+	delete _opt.age;
+	const ctx = {profile, opt: _opt};
+
+	const req = profile.formatJourneysReq(ctx, '8098160', '8000284', new Date('2024-12-07T23:50:12+01:00'), true, null);
+	t.same(req.body, {
+		...berlinWienQuery0,
+		reisendenProfil: {
+			reisende: [
+				{
+					ermaessigungen: [
+						'KEINE_ERMAESSIGUNG KLASSENLOS',
+					],
+					reisendenTyp: 'ERWACHSENER',
+					alter: undefined,
+				},
+			],
+		},
+	});
+	t.end();
+});
+
+
+tap.test('formats a journeys() request with BC correctly (DBnav)', (t) => {
+	const ctx = {profile, opt};
+
+	const req = profile.formatJourneysReq(ctx, '8098160', '8000284', new Date('2024-12-07T23:50:12+01:00'), true, null);
+
+	t.same(req.body, {
+		...berlinWienQuery0,
+		reisendenProfil: {
+			reisende: [
+				{
+					ermaessigungen: [
+						'BAHNCARD25 KLASSE_2',
+					],
+					reisendenTyp: 'JUGENDLICHER',
+					alter: 24,
+				},
+			],
+		},
+	});
+	t.end();
+});
+
+tap.test('formats a journeys() request with unlimited transfers (DBnav)', (t) => {
+	const _opt = {...opt};
+	const ctx = {profile, opt: _opt};
+
+	ctx.opt.transfers = 1; // 1 transfer
+	const reqOneTransfer = profile.formatJourneysReq(ctx, '8098160', '8000284', new Date('2024-12-07T23:50:12+01:00'), true, null);
+	t.equal(reqOneTransfer.body.reiseHin.wunsch.maxUmstiege, 1);
+
+	ctx.opt.transfers = 0; // no transfers
+	const reqZeroTransfers = profile.formatJourneysReq(ctx, '8098160', '8000284', new Date('2024-12-07T23:50:12+01:00'), true, null);
+	t.equal(reqZeroTransfers.body.reiseHin.wunsch.maxUmstiege, 0);
+
+	ctx.opt.transfers = null; // unconstrained transfers implicit
+	const reqUnlimitedTransfersImplicitNull = profile.formatJourneysReq(ctx, '8098160', '8000284', new Date('2024-12-07T23:50:12+01:00'), true, null);
+	t.equal(reqUnlimitedTransfersImplicitNull.body.reiseHin.wunsch.maxUmstiege, undefined);
+
+	ctx.opt.transfers = undefined; // unconstrained transfers implicit
+	const reqUnlimitedTransfersImplicit = profile.formatJourneysReq(ctx, '8098160', '8000284', new Date('2024-12-07T23:50:12+01:00'), true, null);
+	t.equal(reqUnlimitedTransfersImplicit.body.reiseHin.wunsch.maxUmstiege, undefined);
+
+	ctx.opt.transfers = -1; // unconstrained transfers explicit
+	const reqUnlimitedTransfersExplicit = profile.formatJourneysReq(ctx, '8098160', '8000284', new Date('2024-12-07T23:50:12+01:00'), true, null);
+	t.equal(reqUnlimitedTransfersExplicit.body.reiseHin.wunsch.maxUmstiege, undefined);
+
+	t.end();
+});