diff --git a/openpgp-card/src/card_do/extended_length_info.rs b/openpgp-card/src/card_do/extended_length_info.rs
index 8191aa7..4ecea5a 100644
--- a/openpgp-card/src/card_do/extended_length_info.rs
+++ b/openpgp-card/src/card_do/extended_length_info.rs
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: MIT OR Apache-2.0
 
 //! 4.1.3.1 Extended length information
+//! (Introduced in V3.0)
 
 use anyhow::Result;
 use nom::{bytes::complete::tag, number::complete as number, sequence};