diff --git a/chainntnfs/interface.go b/chainntnfs/interface.go
index d589578b..e1e9393d 100644
--- a/chainntnfs/interface.go
+++ b/chainntnfs/interface.go
@@ -36,19 +36,22 @@ type ChainNotifier interface {
 		heightHint uint32) (*ConfirmationEvent, error)
 
 	// RegisterSpendNtfn registers an intent to be notified once the target
-	// outpoint is successfully spent within a confirmed transaction. The
-	// returned SpendEvent will receive a send on the 'Spend' transaction
-	// once a transaction spending the input is detected on the blockchain.
-	// The heightHint parameter is provided as a convenience to light
-	// clients. The heightHint denotes the earliest height in the blockchain
-	// in which the target output could have been created.
+	// outpoint is successfully spent within a transaction. The returned
+	// SpendEvent will receive a send on the 'Spend' transaction once a
+	// transaction spending the input is detected on the blockchain.  The
+	// heightHint parameter is provided as a convenience to light clients.
+	// The heightHint denotes the earliest height in the blockchain in
+	// which the target output could have been created.
 	//
-	// NOTE: This notifications should be triggered once the transaction is
-	// *seen* on the network, not when it has received a single confirmation.
+	// NOTE: If mempool=true is set, then this notification should be
+	// triggered on a best-effort basis once the transaction is *seen* on
+	// the network. If mempool=false, it should only be triggered when the
+	// spending transaction receives a single confirmation.
 	//
 	// NOTE: Dispatching notifications to multiple clients subscribed to a
 	// spend of the same outpoint MUST be supported.
-	RegisterSpendNtfn(outpoint *wire.OutPoint, heightHint uint32) (*SpendEvent, error)
+	RegisterSpendNtfn(outpoint *wire.OutPoint, heightHint uint32,
+		mempool bool) (*SpendEvent, error)
 
 	// RegisterBlockEpochNtfn registers an intent to be notified of each
 	// new block connected to the tip of the main chain. The returned