diff --git a/lib/api/client.dart b/lib/api/client.dart
index f347d38..fca43e5 100644
--- a/lib/api/client.dart
+++ b/lib/api/client.dart
@@ -53,8 +53,15 @@ class Client {
 
   dynamic _handleResponse(http.Response response) {
     if (response.statusCode < 200 ||
-        response.statusCode > 400 ||
+        response.statusCode >= 400 ||
         json == null) {
+      if (response.statusCode ~/ 100 == 4) {
+        Map<String, dynamic> error = _decoder.convert(response.body);
+        throw new InvalidRequestApiException(
+            response.statusCode,
+            response.request.url.toString(),
+            error["message"] ?? "Unknown Error");
+      }
       throw new ApiException(
           response.statusCode, response.request.url.toString());
     }
@@ -62,6 +69,17 @@ class Client {
   }
 }
 
+class InvalidRequestApiException extends ApiException {
+  final String message;
+  InvalidRequestApiException(int errorCode, String path, this.message)
+      : super(errorCode, path);
+
+  @override
+  String toString() {
+    return this.message;
+  }
+}
+
 class ApiException implements Exception {
   final int errorCode;
   final String path;
diff --git a/lib/components/ErrorDialog.dart b/lib/components/ErrorDialog.dart
new file mode 100644
index 0000000..640c3c1
--- /dev/null
+++ b/lib/components/ErrorDialog.dart
@@ -0,0 +1,20 @@
+import 'package:flutter/material.dart';
+
+class ErrorDialog extends StatelessWidget {
+  final dynamic error;
+
+  ErrorDialog({this.error});
+
+  @override
+  Widget build(BuildContext context) {
+    return AlertDialog(
+      content: Text(error.toString()),
+      actions: <Widget>[
+        FlatButton(
+          child: Text('Close'),
+          onPressed: () => Navigator.of(context).maybePop(),
+        )
+      ],
+    );
+  }
+}
diff --git a/lib/main.dart b/lib/main.dart
index 5775d04..440a37a 100644
--- a/lib/main.dart
+++ b/lib/main.dart
@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:sentry/sentry.dart';
 import 'package:vikunja_app/constants.dart';
@@ -9,6 +10,11 @@ import 'package:vikunja_app/pages/user/login.dart';
 import 'package:vikunja_app/theme/theme.dart';
 
 void main() {
+  if (!kReleaseMode) {
+    // only log errors in release mode
+    _startApp();
+    return;
+  }
   var sentry = new SentryClient(dsn: SENTRY_DSN);
 
   FlutterError.onError = (details, {bool forceReport = false}) {
@@ -26,9 +32,7 @@ void main() {
   };
 
   runZoned(
-    () => runApp(VikunjaGlobal(
-        child: new VikunjaApp(home: HomePage()),
-        login: new VikunjaApp(home: LoginPage()))),
+    _startApp,
     onError: (Object error, StackTrace stackTrace) {
       try {
         sentry.captureException(
@@ -44,6 +48,10 @@ void main() {
   );
 }
 
+_startApp() => runApp(VikunjaGlobal(
+    child: new VikunjaApp(home: HomePage()),
+    login: new VikunjaApp(home: LoginPage())));
+
 class VikunjaApp extends StatelessWidget {
   final Widget home;
 
diff --git a/lib/pages/home.dart b/lib/pages/home.dart
index eeeb4b3..0879f16 100644
--- a/lib/pages/home.dart
+++ b/lib/pages/home.dart
@@ -4,6 +4,7 @@ import 'package:flutter/material.dart';
 import 'package:after_layout/after_layout.dart';
 
 import 'package:vikunja_app/components/AddDialog.dart';
+import 'package:vikunja_app/components/ErrorDialog.dart';
 import 'package:vikunja_app/pages/namespace/namespace.dart';
 import 'package:vikunja_app/pages/namespace/namespace_edit.dart';
 import 'package:vikunja_app/pages/placeholder.dart';
@@ -162,7 +163,8 @@ class HomePageState extends State<HomePage> with AfterLayoutMixin<HomePage> {
       Scaffold.of(context).showSnackBar(SnackBar(
         content: Text('The namespace was created successfully!'),
       ));
-    });
+    }).catchError((error) => showDialog(
+            context: context, builder: (context) => ErrorDialog(error: error)));
   }
 
   Future<void> _loadNamespaces() {