diff --git a/rust/protocol/src/proto.rs b/rust/protocol/src/proto.rs
index 04e17edf90..3e330c1a2e 100644
--- a/rust/protocol/src/proto.rs
+++ b/rust/protocol/src/proto.rs
@@ -1,8 +1,10 @@
 //
-// Copyright 2020 Signal Messenger, LLC.
+// Copyright 2020-2021 Signal Messenger, LLC.
 // SPDX-License-Identifier: AGPL-3.0-only
 //
 
+//! Protobuf definitions.
+
 pub mod fingerprint;
 pub mod sealed_sender;
 pub mod storage;