diff --git a/crates/primitives/src/transaction/tx_type.rs b/crates/primitives/src/transaction/tx_type.rs
index 64788e4656..822965a18f 100644
--- a/crates/primitives/src/transaction/tx_type.rs
+++ b/crates/primitives/src/transaction/tx_type.rs
@@ -17,6 +17,12 @@ pub const EIP1559_TX_TYPE_ID: u8 = 2;
 pub(crate) const EIP4844_TX_TYPE_ID: u8 = 3;
 
 /// Transaction Type
+///
+/// Currently being used as 2-bit type when encoding it to [`Compact`] on
+/// [`crate::TransactionSignedNoHash`]. Adding more transaction types will break the codec and
+/// database format.
+///
+/// Other required changes when adding a new type can be seen on [PR#3953](https://github.com/paradigmxyz/reth/pull/3953/files).
 #[derive_arbitrary(compact)]
 #[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Default, Serialize, Deserialize)]
 pub enum TxType {