diff --git a/zebra-consensus/src/transaction.rs b/zebra-consensus/src/transaction.rs
index 52d48442..ae684ae9 100644
--- a/zebra-consensus/src/transaction.rs
+++ b/zebra-consensus/src/transaction.rs
@@ -79,7 +79,8 @@ pub enum Request {
         transaction: Arc<Transaction>,
         /// Additional UTXOs which are known at the time of verification.
         known_utxos: Arc<HashMap<transparent::OutPoint, zs::Utxo>>,
-        /// The active NU in the context of this verification.
+        /// Bug: this field should be the next block height, because some
+        /// consensus rules depend on the exact height. See #1683.
         upgrade: NetworkUpgrade,
     },
 }