diff --git a/src/types.rs b/src/types.rs
index bd6e72ee..7341e3a2 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -1,3 +1,7 @@
+//! Types that extend `imap-types`.
+//!
+//! TODO: Do we really need this?
+
 use std::borrow::Cow;
 
 use imap_types::{