diff --git a/wallet/reservation.c b/wallet/reservation.c
index f7e458c66..4d3b470df 100644
--- a/wallet/reservation.c
+++ b/wallet/reservation.c
@@ -261,17 +261,21 @@ static bool inputs_sufficient(struct amount_sat input,
 	return false;
 }
 
-static struct wally_psbt *psbt_using_utxos(const tal_t *ctx,
-					   struct wallet *wallet,
-					   struct utxo **utxos,
-					   u32 nlocktime,
-					   u32 nsequence)
+struct wally_psbt *psbt_using_utxos(const tal_t *ctx,
+				    struct wallet *wallet,
+				    struct utxo **utxos,
+				    u32 nlocktime,
+				    u32 nsequence,
+				    struct wally_psbt *base)
 {
 	struct pubkey key;
 	u8 *scriptSig, *scriptPubkey, *redeemscript;
 	struct wally_psbt *psbt;
 
-	psbt = create_psbt(ctx, tal_count(utxos), 0, nlocktime);
+	if (base)
+		psbt = base;
+	else
+		psbt = create_psbt(ctx, tal_count(utxos), 0, nlocktime);
 
 	for (size_t i = 0; i < tal_count(utxos); i++) {
 		u32 this_nsequence;
@@ -357,7 +361,8 @@ static struct command_result *finish_psbt(struct command *cmd,
 	}
 
 	psbt = psbt_using_utxos(cmd, cmd->ld->wallet, utxos,
-				*locktime, BITCOIN_TX_RBF_SEQUENCE);
+				*locktime, BITCOIN_TX_RBF_SEQUENCE,
+				NULL);
 	assert(psbt->version == 2);
 	/* Should we add a change output for the excess? */
 	if (excess_as_change) {
diff --git a/wallet/wallet.h b/wallet/wallet.h
index b6c9bb408..5dcf313dd 100644
--- a/wallet/wallet.h
+++ b/wallet/wallet.h
@@ -1748,4 +1748,12 @@ struct wallet_htlc_iter *wallet_htlcs_next(struct wallet *w,
 					   struct amount_msat *msat,
 					   struct sha256 *payment_hash,
 					   enum htlc_state *hstate);
+
+/* Make a PSBT from these utxos, or enhance @base if non-NULL. */
+struct wally_psbt *psbt_using_utxos(const tal_t *ctx,
+				    struct wallet *wallet,
+				    struct utxo **utxos,
+				    u32 nlocktime,
+				    u32 nsequence,
+				    struct wally_psbt *base);
 #endif /* LIGHTNING_WALLET_WALLET_H */