diff --git a/prost-types/src/lib.rs b/prost-types/src/lib.rs
index 863c7e640..77b506873 100644
--- a/prost-types/src/lib.rs
+++ b/prost-types/src/lib.rs
@@ -251,6 +251,7 @@ impl From<std::time::SystemTime> for Timestamp {
     }
 }
 
+/// A timestamp handling error.
 #[derive(Debug, PartialEq)]
 #[non_exhaustive]
 pub enum TimestampError {