diff --git a/includes/controller/shifts_controller.php b/includes/controller/shifts_controller.php
index caf124ba..726814cf 100644
--- a/includes/controller/shifts_controller.php
+++ b/includes/controller/shifts_controller.php
@@ -1,5 +1,6 @@
 <?php
 
+use Engelsystem\Http\Exceptions\HttpForbidden;
 use Engelsystem\ShiftSignupState;
 
 /**
@@ -348,17 +349,18 @@ function shift_next_controller()
 function shifts_json_export_controller()
 {
     $request = request();
+    $user = auth()->apiUser('key');
 
-    if (!$request->has('key') || !preg_match('/^[\da-f]{32}$/', $request->input('key'))) {
-        engelsystem_error('Missing key.');
+    if (
+        !$request->has('key')
+        || !preg_match('/^[\da-f]{32}$/', $request->input('key'))
+        || !$user
+    ) {
+        throw new HttpForbidden('{"error":"Missing or invalid key"}', ['content-type' => 'application/json']);
     }
 
-    $user = auth()->apiUser('key');
-    if (!$user) {
-        engelsystem_error('Key invalid.');
-    }
     if (!auth()->can('shifts_json_export')) {
-        engelsystem_error('No privilege for shifts_json_export.');
+        throw new HttpForbidden('{"error":"Not allowed"}', ['content-type' => 'application/json']);
     }
 
     $shifts = load_ical_shifts();
diff --git a/includes/helper/error_helper.php b/includes/helper/error_helper.php
deleted file mode 100644
index 9314a57a..00000000
--- a/includes/helper/error_helper.php
+++ /dev/null
@@ -1,11 +0,0 @@
-<?php
-
-/**
- * Displays a fatal message and stops execution.
- *
- * @param string $message
- */
-function engelsystem_error($message)
-{
-    raw_output($message);
-}
diff --git a/includes/includes.php b/includes/includes.php
index 855ff359..601a6ca2 100644
--- a/includes/includes.php
+++ b/includes/includes.php
@@ -60,7 +60,6 @@ $includeFiles = [
 
     __DIR__ . '/../includes/helper/graph_helper.php',
     __DIR__ . '/../includes/helper/message_helper.php',
-    __DIR__ . '/../includes/helper/error_helper.php',
     __DIR__ . '/../includes/helper/email_helper.php',
 
     __DIR__ . '/../includes/mailer/shifts_mailer.php',
diff --git a/includes/pages/user_atom.php b/includes/pages/user_atom.php
index 8e5b4858..a491fea7 100644
--- a/includes/pages/user_atom.php
+++ b/includes/pages/user_atom.php
@@ -1,6 +1,7 @@
 <?php
 
 use Engelsystem\Database\DB;
+use Engelsystem\Http\Exceptions\HttpForbidden;
 
 /**
  * Publically available page to feed the news to feed readers
@@ -8,17 +9,18 @@ use Engelsystem\Database\DB;
 function user_atom()
 {
     $request = request();
+    $user = auth()->apiUser('key');
 
-    if (!$request->has('key') || !preg_match('/^[\da-f]{32}$/', $request->input('key'))) {
-        engelsystem_error('Missing key.');
+    if (
+        !$request->has('key')
+        || !preg_match('/^[\da-f]{32}$/', $request->input('key'))
+        || empty($user)
+    ) {
+        throw new HttpForbidden('Missing or invalid key', ['content-type' => 'text/text']);
     }
 
-    $user = auth()->apiUser('key');
-    if (empty($user)) {
-        engelsystem_error('Key invalid.');
-    }
     if (!auth()->can('atom')) {
-        engelsystem_error('No privilege for atom.');
+        throw new HttpForbidden('Not allowed', ['content-type' => 'text/text']);
     }
 
     $news = DB::select('
diff --git a/includes/pages/user_ical.php b/includes/pages/user_ical.php
index ee3a8340..2f3a7ccc 100644
--- a/includes/pages/user_ical.php
+++ b/includes/pages/user_ical.php
@@ -1,22 +1,25 @@
 <?php
 
+use Engelsystem\Http\Exceptions\HttpForbidden;
+
 /**
  * Controller for ical output of users own shifts or any user_shifts filter.
  */
 function user_ical()
 {
     $request = request();
+    $user = auth()->apiUser('key');
 
-    if (!$request->has('key') || !preg_match('/^[\da-f]{32}$/', $request->input('key'))) {
-        engelsystem_error('Missing key.');
+    if (
+        !$request->has('key')
+        || !preg_match('/^[\da-f]{32}$/', $request->input('key'))
+        || !$user
+    ) {
+        throw new HttpForbidden('Missing or invalid key', ['content-type' => 'text/text']);
     }
 
-    $user = auth()->apiUser('key');
-    if (!$user) {
-        engelsystem_error('Key invalid.');
-    }
     if (!auth()->can('ical')) {
-        engelsystem_error('No privilege for ical.');
+        throw new HttpForbidden('Not allowed', ['content-type' => 'text/text']);
     }
 
     $ical_shifts = load_ical_shifts();