diff --git a/index.js b/index.js
index 50408473..19690efb 100644
--- a/index.js
+++ b/index.js
@@ -8,6 +8,7 @@ const pRetry = require('p-retry')
 
 const defaultProfile = require('./lib/default-profile')
 const validateProfile = require('./lib/validate-profile')
+const {INVALID_REQUEST} = require('./lib/errors')
 
 const isNonEmptyString = str => 'string' === typeof str && str.length > 0
 
@@ -241,7 +242,7 @@ const createClient = (profile, userAgent, opt = {}) => {
 
 	const refreshJourney = (refreshToken, opt = {}) => {
 		if ('string' !== typeof refreshToken || !refreshToken) {
-			new TypeError('refreshToken must be a non-empty string.')
+			throw new TypeError('refreshToken must be a non-empty string.')
 		}
 
 		opt = Object.assign({
@@ -307,10 +308,12 @@ const createClient = (profile, userAgent, opt = {}) => {
 		.then(({res, common}) => {
 			if (!res || !Array.isArray(res.locL) || !res.locL[0]) {
 				// todo: proper stack trace?
-				const err = new Error('invalid response')
+				// todo: DRY with lib/request.js
+				const err = new Error('response has no stop')
 				// technically this is not a HAFAS error
 				// todo: find a different flag with decent DX
 				err.isHafasError = true
+				err.code = INVALID_REQUEST
 				throw err
 			}
 
diff --git a/lib/errors.js b/lib/errors.js
index ac1bde41..c370b22c 100644
--- a/lib/errors.js
+++ b/lib/errors.js
@@ -206,10 +206,23 @@ const byErrorCode = Object.assign(Object.create(null), {
 	}
 })
 
+const addErrorInfo = (err, errorCode, errorText, responseId) => {
+	if (byErrorCode[errorCode]) {
+		Object.assign(err, byErrorCode[errorCode])
+		if (errorCode) err.hafasErrorCode = errorCode
+		if (errorText) err.hafasErrorMessage = errorText
+	} else {
+		err.code = errorCode || null
+		err.message = errorText || errorCode || null
+		err.responseId = responseId || null
+	}
+}
+
 module.exports = {
 	ACCESS_DENIED,
 	INVALID_REQUEST,
 	NOT_FOUND,
 	SERVER_ERROR,
-	byErrorCode
+	byErrorCode,
+	addErrorInfo,
 }
diff --git a/lib/request.js b/lib/request.js
index 40b0f611..174c84e6 100644
--- a/lib/request.js
+++ b/lib/request.js
@@ -1,7 +1,7 @@
 'use strict'
 
 const DEV = process.env.NODE_ENV === 'dev'
-const DEBUG = process.env.DEBUG === 'hafas-client'
+const DEBUG = /\bhafas-client\b/.test(process.env.DEBUG || '')
 
 const {randomBytes} = require('crypto')
 const createHash = require('create-hash')
@@ -9,7 +9,7 @@ const captureStackTrace = DEV ? require('capture-stack-trace') : () => {}
 const {stringify} = require('qs')
 const Promise = require('pinkie-promise')
 const {fetch} = require('fetch-ponyfill')({Promise})
-const {byErrorCode} = require('./errors')
+const {addErrorInfo} = require('./errors')
 
 const id = randomBytes(6).toString('hex')
 const randomizeUserAgent = (userAgent) => {
@@ -19,18 +19,6 @@ const randomizeUserAgent = (userAgent) => {
 
 const md5 = input => createHash('md5').update(input).digest()
 
-const addErrorInfo = (err, errorCode, errorText, responseId) => {
-	if (byErrorCode[errorCode]) {
-		Object.assign(err, byErrorCode[errorCode])
-		if (errorCode) err.hafasErrorCode = errorCode
-		if (errorText) err.hafasErrorMessage = errorText
-	} else {
-		err.code = errorCode || null
-		err.message = errorText || errorCode || null
-		err.responseId = responseId || null
-	}
-}
-
 const request = (ctx, userAgent, reqData) => {
 	const {profile, opt} = ctx