diff --git a/metropolis/test/e2e/httpserver/main.go b/metropolis/test/e2e/httpserver/main.go
index 3b593db..be83934 100644
--- a/metropolis/test/e2e/httpserver/main.go
+++ b/metropolis/test/e2e/httpserver/main.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 // httpserver serves a test HTTP endpoint for E2E testing.
 package main