diff --git a/index.js b/index.js
index 69ff8c21..d60098dc 100644
--- a/index.js
+++ b/index.js
@@ -3,14 +3,13 @@
 const minBy = require('lodash/minBy')
 const maxBy = require('lodash/maxBy')
 
+const validateProfile = require('./lib/validate-profile')
 const defaultProfile = require('./lib/default-profile')
 const request = require('./lib/request')
 
 const createClient = (profile) => {
 	profile = Object.assign({}, defaultProfile, profile)
-	if ('string' !== typeof profile.timezone) {
-		throw new Error('profile.timezone must be a string.')
-	}
+	validateProfile(profile)
 
 	const departures = (station, opt = {}) => {
 		if ('string' !== typeof station) throw new Error('station must be a string.')
diff --git a/lib/default-profile.js b/lib/default-profile.js
index 8d673536..418be358 100644
--- a/lib/default-profile.js
+++ b/lib/default-profile.js
@@ -15,7 +15,6 @@ const parseStopover = require('../parse/stopover')
 const formatAddress = require('../format/address')
 const formatCoord = require('../format/coord')
 const formatDate = require('../format/date')
-const filters = require('../format/filters')
 const formatLocationFilter = require('../format/location-filter')
 const formatPoi = require('../format/poi')
 const formatStation = require('../format/station')
@@ -25,7 +24,6 @@ const formatRectangle = require('../format/rectangle')
 
 const id = x => x
 
-// todo: find out which are actually necessary
 const defaultProfile = {
 	transformReqBody: id,
 	transformReq: id,
@@ -48,7 +46,6 @@ const defaultProfile = {
 	formatAddress,
 	formatCoord,
 	formatDate,
-	filters,
 	formatLocationFilter,
 	formatPoi,
 	formatStation,
diff --git a/lib/validate-profile.js b/lib/validate-profile.js
new file mode 100644
index 00000000..7d8b595b
--- /dev/null
+++ b/lib/validate-profile.js
@@ -0,0 +1,43 @@
+'use strict'
+
+const types = {
+	locale: 'string',
+	timezone: 'string',
+	transformReq: 'function',
+	transformReqBody: 'function',
+	transformJourneysQuery: 'function',
+
+	parseDateTime: 'function',
+	parseDeparture: 'function',
+	parseJourneyPart: 'function',
+	parseJourney: 'function',
+	parseLine: 'function',
+	parseStationName: 'function',
+	parseLocation: 'function',
+	parseMovement: 'function',
+	parseNearby: 'function',
+	parseOperator: 'function',
+	parseRemark: 'function',
+	parseStopover: 'function',
+
+	formatAddress: 'function',
+	formatCoord: 'function',
+	formatDate: 'function',
+	formatLocationFilter: 'function',
+	formatPoi: 'function',
+	formatStation: 'function',
+	formatTime: 'function',
+	formatLocation: 'function',
+	formatRectangle: 'function'
+}
+
+const validateProfile = (profile) => {
+	for (let key of Object.keys(types)) {
+		const type = types[key]
+		if (type !== typeof profile[key]) {
+			throw new Error(`profile.${key} must be a ${type}.`)
+		}
+	}
+}
+
+module.exports = validateProfile