diff --git a/Cargo.lock b/Cargo.lock
index 3ab8c72..9c98128 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -154,6 +154,7 @@ dependencies = [
  "anyhow",
  "bdk",
  "bitcoin",
+ "itertools",
  "rand 0.6.5",
  "rand_chacha 0.1.1",
  "secp256k1-zkp",
@@ -206,6 +207,12 @@ dependencies = [
  "lazy_static",
 ]
 
+[[package]]
+name = "either"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+
 [[package]]
 name = "electrum-client"
 version = "0.8.0"
@@ -269,6 +276,15 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "itertools"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69ddb889f9d0d08a67338271fa9b62996bc788c7796a5c18cf057420aaed5eaf"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "0.4.8"
diff --git a/cfd_protocol/Cargo.toml b/cfd_protocol/Cargo.toml
index b900225..f12bf9e 100644
--- a/cfd_protocol/Cargo.toml
+++ b/cfd_protocol/Cargo.toml
@@ -6,6 +6,7 @@ edition = "2018"
 [dependencies]
 anyhow = "1"
 bdk = { git = "https://github.com/bitcoindevkit/bdk/", rev = "acf157a99a305226203d2b55a567291a93c64720" }
+itertools = "0.10"
 rand = "0.6"
 rand_chacha = "0.1"
 secp256k1-zkp = { version = "0.4", features = ["hashes", "global-context"] }
diff --git a/cfd_protocol/src/lib.rs b/cfd_protocol/src/lib.rs
index beb498c..884b914 100644
--- a/cfd_protocol/src/lib.rs
+++ b/cfd_protocol/src/lib.rs
@@ -13,6 +13,7 @@ use bdk::{
     descriptor::Descriptor,
     miniscript::{descriptor::Wsh, DescriptorTrait},
 };
+use itertools::Itertools;
 use secp256k1_zkp::EcdsaAdaptorSignature;
 use secp256k1_zkp::SecretKey;
 use secp256k1_zkp::SECP256K1;
@@ -428,7 +429,7 @@ impl PunishTransaction {
         revoked_commit_tx: &Transaction,
     ) -> Result<Self> {
         // CommitTransaction has only one input
-        let input = revoked_commit_tx.input[0].clone();
+        let input = revoked_commit_tx.input.clone().into_iter().exactly_one()?;
 
         // Extract all signatures from witness stack
         let mut sigs = Vec::new();