diff --git a/api/rest-api.go b/api/rest-api.go
index bd95b1e..85b43c8 100644
--- a/api/rest-api.go
+++ b/api/rest-api.go
@@ -87,7 +87,11 @@ func (api *weatherRestApi) addDataHandler(w http.ResponseWriter, r *http.Request
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
 	}
-	api.addNewWeatherData(data)
+
+	err = api.addNewWeatherData(data)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+	}
 }
 
 func (api *weatherRestApi) homePageHandler(w http.ResponseWriter, r *http.Request) {
@@ -119,6 +123,6 @@ func (api *weatherRestApi) AddNewWeatherDataCallback(callback weathersource.NewW
 	api.weatherSource.AddNewWeatherDataCallback(callback)
 }
 
-func (api *weatherRestApi) addNewWeatherData(weatherData storage.WeatherData) {
-	api.weatherSource.NewWeatherData(weatherData)
+func (api *weatherRestApi) addNewWeatherData(weatherData storage.WeatherData) error {
+	return api.weatherSource.NewWeatherData(weatherData)
 }
diff --git a/main.go b/main.go
index fc0a7c1..9f9559a 100644
--- a/main.go
+++ b/main.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"os"
 	"weather-data/api"
 	"weather-data/config"
@@ -34,8 +35,7 @@ func main() {
 	//setup new weatherData source -> mqtt
 	weatherSource, err = weathersource.NewMqttSource(
 		config.GetMqttUrl(),
-		config.GetMqttTopic(),
-		sensorRegistry)
+		config.GetMqttTopic())
 
 	if err != nil {
 		os.Exit(1)
@@ -54,6 +54,10 @@ func main() {
 	}
 }
 
-func handleNewWeatherData(wd storage.WeatherData) {
+func handleNewWeatherData(wd storage.WeatherData) error {
+	if !config.AllowUnregisteredSensors() && !sensorRegistry.ExistSensorId(wd.SensorId) {
+		return errors.New("sensor have to be registered")
+	}
 	weatherStorage.Save(wd)
+	return nil
 }
diff --git a/weathersource/mqtt-source.go b/weathersource/mqtt-source.go
index 829744e..fe2b774 100644
--- a/weathersource/mqtt-source.go
+++ b/weathersource/mqtt-source.go
@@ -6,7 +6,6 @@ import (
 	"strconv"
 	"strings"
 	"time"
-	"weather-data/config"
 	"weather-data/storage"
 
 	mqtt "github.com/eclipse/paho.mqtt.golang"
@@ -23,7 +22,6 @@ type mqttWeatherSource struct {
 	url                   string
 	topic                 string
 	mqttClient            mqtt.Client
-	sensorRegistry        storage.SensorRegistry
 	lastWeatherDataPoints []*storage.WeatherData
 	weatherSource         WeatherSourceBase
 }
@@ -34,10 +32,9 @@ func (source *mqttWeatherSource) Close() {
 }
 
 //NewMqttSource Factory function for mqttWeatherSource
-func NewMqttSource(url, topic string, sensorRegistry storage.SensorRegistry) (*mqttWeatherSource, error) {
+func NewMqttSource(url, topic string) (*mqttWeatherSource, error) {
 	source := new(mqttWeatherSource)
 	source.url = url
-	source.sensorRegistry = sensorRegistry
 
 	opts := mqtt.NewClientOptions().AddBroker(url)
 
@@ -72,11 +69,6 @@ func (source *mqttWeatherSource) mqttMessageHandler() mqtt.MessageHandler {
 			return
 		}
 
-		if !config.AllowUnregisteredSensors() && !source.sensorRegistry.ExistSensorId(sensorId) {
-			fmt.Println("sensor have to be registered:", sensorId)
-			return
-		}
-
 		lastWeatherData, found := source.getUnwrittenDatapoints(sensorId)
 
 		if !found {
@@ -123,6 +115,6 @@ func (source *mqttWeatherSource) AddNewWeatherDataCallback(callback NewWeatherDa
 	source.weatherSource.AddNewWeatherDataCallback(callback)
 }
 
-func (source *mqttWeatherSource) newWeatherData(datapoint storage.WeatherData) {
-	source.weatherSource.NewWeatherData(datapoint)
+func (source *mqttWeatherSource) newWeatherData(datapoint storage.WeatherData) error {
+	return source.weatherSource.NewWeatherData(datapoint)
 }
diff --git a/weathersource/weather-source.go b/weathersource/weather-source.go
index f5ddd00..18a6772 100644
--- a/weathersource/weather-source.go
+++ b/weathersource/weather-source.go
@@ -3,7 +3,7 @@ package weathersource
 import "weather-data/storage"
 
 //NewWeatherDataCallbackFunc Function-Signature for new weather data callback function
-type NewWeatherDataCallbackFunc func(storage.WeatherData)
+type NewWeatherDataCallbackFunc func(storage.WeatherData) error
 
 //WeatherSource is the interface for different weather-source implementations
 type WeatherSource interface {
@@ -22,8 +22,12 @@ func (source *WeatherSourceBase) AddNewWeatherDataCallback(callback NewWeatherDa
 }
 
 //NewWeatherData executes all newWeatherDataCallbackFuncs for this datapoint
-func (source *WeatherSourceBase) NewWeatherData(datapoint storage.WeatherData) {
+func (source *WeatherSourceBase) NewWeatherData(datapoint storage.WeatherData) error {
 	for _, callback := range source.newWeatherDataCallbackFuncs {
-		callback(datapoint)
+		err := callback(datapoint)
+		if err != nil {
+			return err
+		}
 	}
+	return nil
 }