diff --git a/src/InvalidStateError.php b/src/InvalidStateError.php
new file mode 100644
index 0000000..d822bda
--- /dev/null
+++ b/src/InvalidStateError.php
@@ -0,0 +1,11 @@
+<?php
+
+/*
+ * PHP-Auth (https://github.com/delight-im/PHP-Auth)
+ * Copyright (c) delight.im (https://www.delight.im/)
+ * Licensed under the MIT License (https://opensource.org/licenses/MIT)
+ */
+
+namespace Delight\Auth;
+
+class InvalidStateError extends AuthError {}