diff --git a/lnwallet/script_utils.go b/lnwallet/script_utils.go
index 3eafcba1..114e9b3b 100644
--- a/lnwallet/script_utils.go
+++ b/lnwallet/script_utils.go
@@ -83,7 +83,7 @@ func GenFundingPkScript(aPub, bPub []byte, amt int64) ([]byte, *wire.TxOut, erro
 	return redeemScript, wire.NewTxOut(amt, pkScript), nil
 }
 
-// spendMultiSig generates the witness stack required to redeem the 2-of-2 p2wsh
+// SpendMultiSig generates the witness stack required to redeem the 2-of-2 p2wsh
 // multi-sig output.
 func SpendMultiSig(redeemScript, pubA, sigA, pubB, sigB []byte) [][]byte {
 	witness := make([][]byte, 4)
@@ -592,18 +592,19 @@ func commitScriptUnencumbered(key *btcec.PublicKey) ([]byte, error) {
 	return builder.Script()
 }
 
-// commitSpendTimeout constructs a valid witness allowing the owner of a
+// CommitSpendTimeout constructs a valid witness allowing the owner of a
 // particular commitment transaction to spend the output returning settled
 // funds back to themselves after an absolute block timeout.
-func commitSpendTimeout(commitScript []byte, outputAmt btcutil.Amount,
-	blockTimeout uint32, selfKey *btcec.PrivateKey,
-	sweepTx *wire.MsgTx) (wire.TxWitness, error) {
+func CommitSpendTimeout(signer Signer, signDesc *SignDescriptor,
+	blockTimeout uint32, sweepTx *wire.MsgTx) (wire.TxWitness, error) {
+
+	inputIndex := signDesc.InputIndex
 
 	// In order to properly spend the transaction, we need to set the
 	// sequence number. We do this by convering the relative block delay
 	// into a sequence number value able to be interpeted by
 	// OP_CHECKSEQUENCEVERIFY.
-	sweepTx.TxIn[0].Sequence = lockTimeToSequence(false, blockTimeout)
+	sweepTx.TxIn[inputIndex].Sequence = lockTimeToSequence(false, blockTimeout)
 
 	// Additionally, OP_CSV requires that the version of the transaction
 	// spending a pkscript with OP_CSV within it *must* be >= 2.
@@ -611,10 +612,7 @@ func commitSpendTimeout(commitScript []byte, outputAmt btcutil.Amount,
 
 	// With the sequence number in place, we're now able to properly sign
 	// off on the sweep transaction.
-	hashCache := txscript.NewTxSigHashes(sweepTx)
-	sweepSig, err := txscript.RawTxInWitnessSignature(
-		sweepTx, hashCache, 0, int64(outputAmt), commitScript,
-		txscript.SigHashAll, selfKey)
+	sweepSig, err := signer.SignOutputRaw(sweepTx, signDesc)
 	if err != nil {
 		return nil, err
 	}
@@ -622,9 +620,9 @@ func commitSpendTimeout(commitScript []byte, outputAmt btcutil.Amount,
 	// Place a zero as the first item in the evaluated witness stack to
 	// force script execution to the timeout spend clause.
 	witnessStack := wire.TxWitness(make([][]byte, 3))
-	witnessStack[0] = sweepSig
+	witnessStack[0] = append(sweepSig, byte(txscript.SigHashAll))
 	witnessStack[1] = []byte{0}
-	witnessStack[2] = commitScript
+	witnessStack[2] = signDesc.RedeemScript
 
 	return witnessStack, nil
 }
diff --git a/lnwallet/script_utils_test.go b/lnwallet/script_utils_test.go
index 1952d174..665a1ff4 100644
--- a/lnwallet/script_utils_test.go
+++ b/lnwallet/script_utils_test.go
@@ -43,6 +43,8 @@ func TestCommitmentSpendValidation(t *testing.T) {
 	revocationPreimage := testHdSeed[:]
 	revokePubKey := DeriveRevocationPubkey(bobKeyPub, revocationPreimage)
 
+	aliceSelfOutputSigner := &mockSigner{aliceKeyPriv}
+
 	// With all the test data set up, we create the commitment transaction.
 	// We only focus on a single party's transactions, as the scripts are
 	// identical with the roles reversed.
@@ -77,15 +79,24 @@ func TestCommitmentSpendValidation(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unable to generate alice delay script: %v")
 	}
-	aliceWitnessSpend, err := commitSpendTimeout(delayScript, channelBalance,
-		csvTimeout, aliceKeyPriv, sweepTx)
+	signDesc := &SignDescriptor{
+		RedeemScript: delayScript,
+		SigHashes:    txscript.NewTxSigHashes(sweepTx),
+		Output: &wire.TxOut{
+			Value: int64(channelBalance),
+		},
+		HashType:   txscript.SigHashAll,
+		InputIndex: 0,
+	}
+	aliceWitnessSpend, err := CommitSpendTimeout(aliceSelfOutputSigner,
+		signDesc, csvTimeout, sweepTx)
 	if err != nil {
 		t.Fatalf("unable to generate delay commit spend witness :%v")
 	}
 	sweepTx.TxIn[0].Witness = aliceWitnessSpend
 	vm, err := txscript.NewEngine(delayOutput.PkScript,
 		sweepTx, 0, txscript.StandardVerifyFlags, nil,
-		nil, int64(channelBalance))
+		signDesc.SigHashes, int64(channelBalance))
 	if err != nil {
 		t.Fatalf("unable to create engine: %v", err)
 	}