diff --git a/src/chain/mod.rs b/src/chain/mod.rs
index 92c4bdb64..5a326be97 100644
--- a/src/chain/mod.rs
+++ b/src/chain/mod.rs
@@ -9,7 +9,7 @@ pub(crate) mod bitcoind;
 mod electrum;
 mod esplora;
 
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
@@ -84,7 +84,7 @@ impl WalletSyncStatus {
 
 pub(crate) struct ChainSource {
 	kind: ChainSourceKind,
-	registered_txids: Mutex<Vec<Txid>>,
+	registered_txids: Mutex<HashSet<Txid>>,
 	tx_broadcaster: Arc<Broadcaster>,
 	logger: Arc<Logger>,
 }
@@ -113,7 +113,7 @@ impl ChainSource {
 			node_metrics,
 		)?;
 		let kind = ChainSourceKind::Esplora(esplora_chain_source);
-		let registered_txids = Mutex::new(Vec::new());
+		let registered_txids = Mutex::new(HashSet::new());
 		Ok((Self { kind, registered_txids, tx_broadcaster, logger }, None))
 	}
 
@@ -133,7 +133,7 @@ impl ChainSource {
 			node_metrics,
 		);
 		let kind = ChainSourceKind::Electrum(electrum_chain_source);
-		let registered_txids = Mutex::new(Vec::new());
+		let registered_txids = Mutex::new(HashSet::new());
 		(Self { kind, registered_txids, tx_broadcaster, logger }, None)
 	}
 
@@ -156,7 +156,7 @@ impl ChainSource {
 		);
 		let best_block = bitcoind_chain_source.poll_best_block().await.ok();
 		let kind = ChainSourceKind::Bitcoind(bitcoind_chain_source);
-		let registered_txids = Mutex::new(Vec::new());
+		let registered_txids = Mutex::new(HashSet::new());
 		(Self { kind, registered_txids, tx_broadcaster, logger }, best_block)
 	}
 
@@ -180,7 +180,7 @@ impl ChainSource {
 		);
 		let best_block = bitcoind_chain_source.poll_best_block().await.ok();
 		let kind = ChainSourceKind::Bitcoind(bitcoind_chain_source);
-		let registered_txids = Mutex::new(Vec::new());
+		let registered_txids = Mutex::new(HashSet::new());
 		(Self { kind, registered_txids, tx_broadcaster, logger }, best_block)
 	}
 
@@ -214,7 +214,7 @@ impl ChainSource {
 		}
 	}
 
-	pub(crate) fn registered_txids(&self) -> Vec<Txid> {
+	pub(crate) fn registered_txids(&self) -> HashSet<Txid> {
 		self.registered_txids.lock().expect("lock").clone()
 	}
 
@@ -472,7 +472,7 @@ impl ChainSource {
 
 impl Filter for ChainSource {
 	fn register_tx(&self, txid: &Txid, script_pubkey: &Script) {
-		self.registered_txids.lock().expect("lock").push(*txid);
+		self.registered_txids.lock().expect("lock").insert(*txid);
 		match &self.kind {
 			ChainSourceKind::Esplora(esplora_chain_source) => {
 				esplora_chain_source.register_tx(txid, script_pubkey)
diff --git a/src/payment/bolt11.rs b/src/payment/bolt11.rs
index 068269997..e3cb948a1 100644
--- a/src/payment/bolt11.rs
+++ b/src/payment/bolt11.rs
@@ -539,7 +539,7 @@ impl Bolt11Payment {
 				_ => 0,
 			};
 			if let Some(invoice_amount_msat) = details.amount_msat {
-				if claimable_amount_msat < invoice_amount_msat - skimmed_fee_msat {
+				if claimable_amount_msat < invoice_amount_msat.saturating_sub(skimmed_fee_msat) {
 					log_error!(
 						self.logger,
 						"Failed to manually claim payment {} as the claimable amount is less than expected",
diff --git a/src/payment/unified.rs b/src/payment/unified.rs
index 3708afe8e..2ad77f772 100644
--- a/src/payment/unified.rs
+++ b/src/payment/unified.rs
@@ -129,9 +129,9 @@ impl UnifiedPayment {
 	pub fn receive(
 		&self, amount_sats: u64, description: &str, expiry_sec: u32,
 	) -> Result<String, Error> {
-		let onchain_address = self.onchain_payment.new_address()?;
+		let amount_msats = amount_sats.checked_mul(1_000).ok_or(Error::InvalidAmount)?;
 
-		let amount_msats = amount_sats * 1_000;
+		let onchain_address = self.onchain_payment.new_address()?;
 
 		let bolt12_offer =
 			match self.bolt12_payment.receive_inner(amount_msats, description, None, None) {
diff --git a/tests/integration_tests_rust.rs b/tests/integration_tests_rust.rs
index 309d5bf4d..76835b38a 100644
--- a/tests/integration_tests_rust.rs
+++ b/tests/integration_tests_rust.rs
@@ -1680,6 +1680,18 @@ async fn generate_bip21_uri() {
 	assert!(uni_payment.contains("lno="));
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 1)]
+async fn unified_receive_rejects_msat_overflow() {
+	let (bitcoind, electrsd) = setup_bitcoind_and_electrsd();
+	let chain_source = random_chain_source(&bitcoind, &electrsd);
+	let node = setup_node(&chain_source, random_config(true));
+
+	assert_eq!(
+		Err(NodeError::InvalidAmount),
+		node.unified_payment().receive(u64::MAX, "asdf", 4_000)
+	);
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 1)]
 async fn unified_send_receive_bip21_uri() {
 	let (bitcoind, electrsd) = setup_bitcoind_and_electrsd();