diff --git a/static_src/shared/errors.js b/static_src/shared/errors.js
new file mode 100644
index 0000000..81c0035
--- /dev/null
+++ b/static_src/shared/errors.js
@@ -0,0 +1,9 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+export class UserInputError extends Error {
+  get name() {
+    return 'UserInputError';
+  }
+}