diff --git a/app/DomainRepository/DatabaseDomainRepository.php b/app/DomainRepository/DatabaseDomainRepository.php
index 24474af..43ae237 100644
--- a/app/DomainRepository/DatabaseDomainRepository.php
+++ b/app/DomainRepository/DatabaseDomainRepository.php
@@ -79,8 +79,8 @@ public function storeDomain(array $data): PromiseInterface
         $this->getDomainByName($data['domain'])
             ->then(function ($registeredDomain) use ($data, $deferred) {
                 $this->database->query("
-                    INSERT INTO domains (user_id, domain, created_at)
-                    VALUES (:user_id, :domain, DATETIME('now'))
+                    INSERT INTO domains (user_id, domain, error_page, created_at)
+                    VALUES (:user_id, :domain, :error_page, DATETIME('now'))
                 ", $data)
                     ->then(function (Result $result) use ($deferred) {
                         $this->database->query('SELECT * FROM domains WHERE id = :id', ['id' => $result->insertId])
@@ -128,7 +128,15 @@ public function updateDomain($id, array $data): PromiseInterface
     {
         $deferred = new Deferred();
 
-        // TODO
+        $this->database->query('UPDATE domains SET error_page = :error_page WHERE (id = :id OR domain = :id)', array_merge($data, [
+            'id' => $id,
+        ]))
+            ->then(function (Result $result) use ($deferred, $id) {
+                $this->getDomainById($id)
+                    ->then(function ($domain) use ($deferred) {
+                        $deferred->resolve($domain);
+                    });
+            });
 
         return $deferred->promise();
     }
diff --git a/app/Factory.php b/app/Factory.php
index 175213a..58bddb0 100644
--- a/app/Factory.php
+++ b/app/Factory.php
@@ -32,6 +32,7 @@
 use Expose\Server\Http\Controllers\Admin\StoreSettingsController;
 use Expose\Server\Http\Controllers\Admin\StoreSubdomainController;
 use Expose\Server\Http\Controllers\Admin\StoreUsersController;
+use Expose\Server\Http\Controllers\Admin\UpdateDomainController;
 use Expose\Server\Http\Controllers\ControlMessageController;
 use Expose\Server\Http\Controllers\HealthController;
 use Expose\Server\Http\Controllers\TunnelMessageController;
@@ -160,6 +161,7 @@ protected function addAdminRoutes()
         $this->router->get('/api/logs/{subdomain}', GetLogsForSubdomainController::class, $adminCondition);
 
         $this->router->post('/api/domains', StoreDomainController::class, $adminCondition);
+        $this->router->put('/api/domains/{id}', UpdateDomainController::class, $adminCondition);
         $this->router->delete('/api/domains/{domain}', DeleteSubdomainController::class, $adminCondition);
 
         $this->router->post('/api/subdomains', StoreSubdomainController::class, $adminCondition);
diff --git a/app/Http/Controllers/Admin/StoreDomainController.php b/app/Http/Controllers/Admin/StoreDomainController.php
index 5c5b2c1..f900191 100644
--- a/app/Http/Controllers/Admin/StoreDomainController.php
+++ b/app/Http/Controllers/Admin/StoreDomainController.php
@@ -28,6 +28,7 @@ public function handle(Request $request, ConnectionInterface $httpConnection)
     {
         $validator = Validator::make($request->all(), [
             'domain' => 'required',
+            'error_page' => 'nullable|string'
         ], [
             'required' => 'The :attribute field is required.',
         ]);
@@ -59,6 +60,7 @@ public function handle(Request $request, ConnectionInterface $httpConnection)
                 $insertData = [
                     'user_id' => $user['id'],
                     'domain' => $request->get('domain'),
+                    'error_page' => $request->get('error_page'),
                 ];
 
                 $this->domainRepository
diff --git a/app/Http/Controllers/Admin/UpdateDomainController.php b/app/Http/Controllers/Admin/UpdateDomainController.php
new file mode 100644
index 0000000..eb06344
--- /dev/null
+++ b/app/Http/Controllers/Admin/UpdateDomainController.php
@@ -0,0 +1,71 @@
+<?php
+
+namespace Expose\Server\Http\Controllers\Admin;
+
+use Expose\Server\Contracts\DomainRepository;
+use Expose\Server\Contracts\UserRepository;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Validator;
+use Ratchet\ConnectionInterface;
+
+class UpdateDomainController extends AdminController
+{
+    protected $keepConnectionOpen = true;
+
+    /** @var DomainRepository */
+    protected $domainRepository;
+
+    /** @var UserRepository */
+    protected $userRepository;
+
+    public function __construct(UserRepository $userRepository, DomainRepository $domainRepository)
+    {
+        $this->userRepository = $userRepository;
+        $this->domainRepository = $domainRepository;
+    }
+
+    public function handle(Request $request, ConnectionInterface $httpConnection)
+    {
+        $id = $request->get('id');
+
+        $validator = Validator::make($request->all(), [
+            'error_page' => 'nullable|string'
+        ]);
+
+        if ($validator->fails()) {
+            $httpConnection->send(respond_json(['errors' => $validator->getMessageBag()], 401));
+            $httpConnection->close();
+
+            return;
+        }
+
+        $this->userRepository
+            ->getUserByToken($request->get('auth_token', ''))
+            ->then(function ($user) use ($httpConnection, $request, $id) {
+                if (is_null($user)) {
+                    $httpConnection->send(respond_json(['error' => 'The user does not exist'], 404));
+                    $httpConnection->close();
+
+                    return;
+                }
+
+                if ($user['can_specify_domains'] === 0) {
+                    $httpConnection->send(respond_json(['error' => 'The user is not allowed to reserve custom domains.'], 401));
+                    $httpConnection->close();
+
+                    return;
+                }
+
+                $updateData = [
+                    'error_page' => $request->get('error_page'),
+                ];
+
+                $this->domainRepository
+                    ->updateDomain($id, $updateData)
+                    ->then(function ($domain) use ($httpConnection) {
+                        $httpConnection->send(respond_json(['domain' => $domain], 200));
+                        $httpConnection->close();
+                    });
+            });
+    }
+}
diff --git a/app/Http/Controllers/TunnelMessageController.php b/app/Http/Controllers/TunnelMessageController.php
index cdf2c21..34d597e 100644
--- a/app/Http/Controllers/TunnelMessageController.php
+++ b/app/Http/Controllers/TunnelMessageController.php
@@ -6,6 +6,7 @@
 use Expose\Server\Connections\ControlConnection;
 use Expose\Server\Connections\HttpConnection;
 use Expose\Server\Contracts\ConnectionManager;
+use Expose\Server\Contracts\DomainRepository;
 use Expose\Server\Contracts\StatisticsCollector;
 use Expose\Common\Http\Controllers\Controller;
 use GuzzleHttp\Psr7\Message;
@@ -31,11 +32,15 @@ class TunnelMessageController extends Controller
     /** @var StatisticsCollector */
     protected $statisticsCollector;
 
-    public function __construct(ConnectionManager $connectionManager, StatisticsCollector $statisticsCollector, Configuration $configuration)
+    /** @var DomainRepository */
+    protected $domainRepository;
+
+    public function __construct(ConnectionManager $connectionManager, StatisticsCollector $statisticsCollector, Configuration $configuration, DomainRepository $domainRepository)
     {
         $this->connectionManager = $connectionManager;
         $this->configuration = $configuration;
         $this->statisticsCollector = $statisticsCollector;
+        $this->domainRepository = $domainRepository;
     }
 
     public function handle(Request $request, ConnectionInterface $httpConnection)
@@ -55,11 +60,24 @@ public function handle(Request $request, ConnectionInterface $httpConnection)
         $controlConnection = $this->connectionManager->findControlConnectionForSubdomainAndServerHost($subdomain, $serverHost);
 
         if (is_null($controlConnection)) {
-            $httpConnection->send(
-                respond_html($this->getBlade($httpConnection, 'server.errors.404', ['subdomain' => $subdomain]), 404)
-            );
-            $httpConnection->close();
-
+            $this->domainRepository
+                ->getDomainByName(strtolower($serverHost))
+                ->then(function ($domain) use ($subdomain, $httpConnection) {
+                    if (is_null($domain) || is_null($domain['error_page'])) {
+                        $errorPageContent = $this->getBlade($httpConnection, 'server.errors.404', ['subdomain' => $subdomain]);
+                    } else {
+                        $errorPageContent = str_replace(
+                            ['%%subdomain%%'],
+                            [$subdomain],
+                            $domain['error_page']
+                        );
+                    }
+
+                    $httpConnection->send(
+                        respond_html($errorPageContent, 404)
+                    );
+                    $httpConnection->close();
+                });
             return;
         }
 
diff --git a/database/migrations/12_add_404_to_domains_table.sql b/database/migrations/12_add_404_to_domains_table.sql
new file mode 100644
index 0000000..d27a0f7
--- /dev/null
+++ b/database/migrations/12_add_404_to_domains_table.sql
@@ -0,0 +1 @@
+ALTER TABLE domains ADD COLUMN error_page TEXT DEFAULT NULL;
\ No newline at end of file
diff --git a/tests/Feature/Server/TunnelTest.php b/tests/Feature/Server/TunnelTest.php
index 0513c8c..6650ad1 100644
--- a/tests/Feature/Server/TunnelTest.php
+++ b/tests/Feature/Server/TunnelTest.php
@@ -78,6 +78,109 @@ public function it_returns_404_for_non_existing_clients_on_custom_hosts()
         ]));
     }
 
+    /** @test */
+    public function it_returns_default_404_pages_for_custom_domains_when_no_custom_error_page_is_specified()
+    {
+        $this->app['config']['expose-server.validate_auth_tokens'] = true;
+
+        $user = $this->createUser([
+            'name' => 'Marcel',
+            'can_specify_domains' => 1,
+        ]);
+
+        $this->await($this->browser->post('http://127.0.0.1:8080/api/domains', [
+            'Host' => 'expose.localhost',
+            'Authorization' => base64_encode('username:secret'),
+            'Content-Type' => 'application/json',
+        ], json_encode([
+            'domain' => 'share.beyondco.de',
+            'auth_token' => $user->auth_token,
+        ])));
+
+        try {
+            $this->await($this->browser->get('http://127.0.0.1:8080/', [
+                'Host' => 'tunnel.share.beyondco.de',
+            ]));
+        } catch (ResponseException $e) {
+            $response = $e->getResponse();
+
+            $this->assertStringContainsString('<title>Expose</title>', $response->getBody()->getContents());
+        }
+    }
+
+    /** @test */
+    public function it_returns_custom_404_pages_for_custom_domains_when_specified()
+    {
+        $this->app['config']['expose-server.validate_auth_tokens'] = true;
+
+        $user = $this->createUser([
+            'name' => 'Marcel',
+            'can_specify_domains' => 1,
+        ]);
+
+        $this->await($this->browser->post('http://127.0.0.1:8080/api/domains', [
+            'Host' => 'expose.localhost',
+            'Authorization' => base64_encode('username:secret'),
+            'Content-Type' => 'application/json',
+        ], json_encode([
+            'domain' => 'share.beyondco.de',
+            'error_page' => '<h1>Custom 404 for %%subdomain%%</h1>',
+            'auth_token' => $user->auth_token,
+        ])));
+
+        try {
+            $this->await($this->browser->get('http://127.0.0.1:8080/', [
+                'Host' => 'tunnel.share.beyondco.de',
+            ]));
+        } catch (ResponseException $e) {
+            $response = $e->getResponse();
+
+            $this->assertStringContainsString('<h1>Custom 404 for tunnel</h1>', $response->getBody()->getContents());
+        }
+    }
+
+    /** @test */
+    public function it_can_update_404_pages_for_custom_domains()
+    {
+        $this->app['config']['expose-server.validate_auth_tokens'] = true;
+
+        $user = $this->createUser([
+            'name' => 'Marcel',
+            'can_specify_domains' => 1,
+        ]);
+
+        $domainResponse = $this->await($this->browser->post('http://127.0.0.1:8080/api/domains', [
+            'Host' => 'expose.localhost',
+            'Authorization' => base64_encode('username:secret'),
+            'Content-Type' => 'application/json',
+        ], json_encode([
+            'domain' => 'share.beyondco.de',
+            'auth_token' => $user->auth_token,
+        ])));
+
+        $domain = json_decode($domainResponse->getBody()->getContents())->domain;
+
+        $this->await($this->browser->put('http://127.0.0.1:8080/api/domains/'.$domain->id, [
+            'Host' => 'expose.localhost',
+            'Authorization' => base64_encode('username:secret'),
+            'Content-Type' => 'application/json',
+        ], json_encode([
+            'domain' => 'share.beyondco.de',
+            'error_page' => '<h1>Custom 404 for %%subdomain%%</h1>',
+            'auth_token' => $user->auth_token,
+        ])));
+
+        try {
+            $this->await($this->browser->get('http://127.0.0.1:8080/', [
+                'Host' => 'tunnel.share.beyondco.de',
+            ]));
+        } catch (ResponseException $e) {
+            $response = $e->getResponse();
+
+            $this->assertStringContainsString('<h1>Custom 404 for tunnel</h1>', $response->getBody()->getContents());
+        }
+    }
+
     /** @test */
     public function it_sends_incoming_requests_to_the_connected_client()
     {