diff --git a/src/blockdata/transaction.rs b/src/blockdata/transaction.rs
index b41580f..30d645b 100644
--- a/src/blockdata/transaction.rs
+++ b/src/blockdata/transaction.rs
@@ -241,7 +241,7 @@ impl Default for TxOut {
 /// for 0-input transactions, which results in unambiguously parseable transactions.
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct Transaction {
-    /// The protocol version, should always be 1.
+    /// The protocol version, is currently expected to be 1 or 2 (BIP 68).
     pub version: u32,
     /// Block number before which this transaction is valid, or 0 for
     /// valid immediately.