diff --git a/src/Auth/AuthMiddleware.php b/src/Auth/AuthMiddleware.php
index 6738f6e..e32fd38 100644
--- a/src/Auth/AuthMiddleware.php
+++ b/src/Auth/AuthMiddleware.php
@@ -21,8 +21,7 @@ class AuthMiddleware implements MiddlewareInterface
         // TODO: Lots of stuff. Session middleware, auth handler class, etc...
         if ($uri->getPath() !== '/login') {
             // Check authorization via session
-            // TODO username or user ID?
-            if (empty($_SESSION['username'])) {
+            if (empty($_SESSION['user_id'])) {
                 // Not logged in -> Redirect to /login
                 $response = new Response();
                 return $response
diff --git a/src/Common/UserHelper.php b/src/Common/UserHelper.php
index e67f56b..9d65b55 100644
--- a/src/Common/UserHelper.php
+++ b/src/Common/UserHelper.php
@@ -19,15 +19,15 @@ class UserHelper
 
     public function isLoggedIn(): bool
     {
-        return !empty($_SESSION['username']);
+        return !empty($_SESSION['user_id']);
     }
 
     public function getCurrentUser(): AdminUser
     {
-        $username = $_SESSION['username'] ?? null;
-        if (empty($username)) {
+        $userId = $_SESSION['user_id'] ?? null;
+        if (empty($userId)) {
             throw new RuntimeException('Not logged in!');
         }
-        return $this->adminUserRepository->getUserByName($username);
+        return $this->adminUserRepository->getUserById($userId);
     }
 }
diff --git a/src/Frontend/Login/LoginController.php b/src/Frontend/Login/LoginController.php
index 73899d9..c3695fb 100644
--- a/src/Frontend/Login/LoginController.php
+++ b/src/Frontend/Login/LoginController.php
@@ -66,7 +66,7 @@ class LoginController extends BaseController
         }
 
         // Set login session
-        $_SESSION['username'] = $user->getUsername();
+        $_SESSION['user_id'] = $user->getId();
         return $response
             ->withHeader('Location', '/')
             ->withStatus(303);
diff --git a/src/Repositories/AdminUserRepository.php b/src/Repositories/AdminUserRepository.php
index 31e2a41..84376f5 100644
--- a/src/Repositories/AdminUserRepository.php
+++ b/src/Repositories/AdminUserRepository.php
@@ -17,6 +17,22 @@ class AdminUserRepository
         $this->pdo = $pdo;
     }
 
+    /**
+     * @throws AdminUserNotFoundException
+     */
+    public function getUserById(int $userId): AdminUser
+    {
+        $statement = $this->pdo->prepare('SELECT * FROM admin_users WHERE admin_id = :admin_id LIMIT 1');
+        $statement->execute(['admin_id' => $userId]);
+
+        if ($statement->rowCount() < 1) {
+            throw new AdminUserNotFoundException("Admin with ID '$userId' was not found.");
+        }
+
+        $row = $statement->fetch(PDO::FETCH_ASSOC);
+        return AdminUser::createFromArray($row);
+    }
+
     /**
      * @throws AdminUserNotFoundException
      */