diff --git a/src/interfaces/wallet.h b/src/interfaces/wallet.h
index 9fc8ab0ef51..89477aa16d1 100644
--- a/src/interfaces/wallet.h
+++ b/src/interfaces/wallet.h
@@ -204,7 +204,7 @@ public:
         int& num_blocks) = 0;
 
     //! Fill PSBT.
-    virtual std::optional<common::PSBTError> fillPSBT(int sighash_type,
+    virtual std::optional<common::PSBTError> fillPSBT(std::optional<int> sighash_type,
         bool sign,
         bool bip32derivs,
         size_t* n_signed,
diff --git a/src/qt/psbtoperationsdialog.cpp b/src/qt/psbtoperationsdialog.cpp
index 454d9287aea..afe6a8999ac 100644
--- a/src/qt/psbtoperationsdialog.cpp
+++ b/src/qt/psbtoperationsdialog.cpp
@@ -59,7 +59,7 @@ void PSBTOperationsDialog::openWithPSBT(PartiallySignedTransaction psbtx)
     bool complete = FinalizePSBT(psbtx); // Make sure all existing signatures are fully combined before checking for completeness.
     if (m_wallet_model) {
         size_t n_could_sign;
-        const auto err{m_wallet_model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/true, &n_could_sign, m_transaction_data, complete)};
+        const auto err{m_wallet_model->wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/true, &n_could_sign, m_transaction_data, complete)};
         if (err) {
             showStatus(tr("Failed to load transaction: %1")
                            .arg(QString::fromStdString(PSBTErrorString(*err).translated)),
@@ -83,7 +83,7 @@ void PSBTOperationsDialog::signTransaction()
 
     WalletModel::UnlockContext ctx(m_wallet_model->requestUnlock());
 
-    const auto err{m_wallet_model->wallet().fillPSBT(SIGHASH_DEFAULT, /*sign=*/true, /*bip32derivs=*/true, &n_signed, m_transaction_data, complete)};
+    const auto err{m_wallet_model->wallet().fillPSBT(std::nullopt, /*sign=*/true, /*bip32derivs=*/true, &n_signed, m_transaction_data, complete)};
 
     if (err) {
         showStatus(tr("Failed to sign transaction: %1")
@@ -251,7 +251,7 @@ size_t PSBTOperationsDialog::couldSignInputs(const PartiallySignedTransaction &p
 
     size_t n_signed;
     bool complete;
-    const auto err{m_wallet_model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/false, &n_signed, m_transaction_data, complete)};
+    const auto err{m_wallet_model->wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/false, &n_signed, m_transaction_data, complete)};
 
     if (err) {
         return 0;
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index b8a9854f0e0..c2ebb875de6 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -450,7 +450,7 @@ void SendCoinsDialog::presentPSBT(PartiallySignedTransaction& psbtx)
 bool SendCoinsDialog::signWithExternalSigner(PartiallySignedTransaction& psbtx, CMutableTransaction& mtx, bool& complete) {
     std::optional<PSBTError> err;
     try {
-        err = model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/true, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete);
+        err = model->wallet().fillPSBT(std::nullopt, /*sign=*/true, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete);
     } catch (const std::runtime_error& e) {
         QMessageBox::critical(nullptr, tr("Sign failed"), e.what());
         return false;
@@ -507,7 +507,7 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
         PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
         // Fill without signing
-        const auto err{model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete)};
+        const auto err{model->wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete)};
         assert(!complete);
         assert(!err);
 
@@ -523,7 +523,7 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
             bool complete = false;
             // Always fill without signing first. This prevents an external signer
             // from being called prematurely and is not expensive.
-            const auto err{model->wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete)};
+            const auto err{model->wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete)};
             assert(!complete);
             assert(!err);
             send_failure = !signWithExternalSigner(psbtx, mtx, complete);
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index 07d5b9413c3..4483144582f 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -519,7 +519,7 @@ bool WalletModel::bumpFee(uint256 hash, uint256& new_hash)
         // "Create Unsigned" clicked
         PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
-        const auto err{wallet().fillPSBT(SIGHASH_ALL, /*sign=*/false, /*bip32derivs=*/true, nullptr, psbtx, complete)};
+        const auto err{wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/true, nullptr, psbtx, complete)};
         if (err || complete) {
             QMessageBox::critical(nullptr, tr("Fee bump error"), tr("Can't draft transaction."));
             return false;
diff --git a/src/wallet/external_signer_scriptpubkeyman.cpp b/src/wallet/external_signer_scriptpubkeyman.cpp
index 32e9941453b..7268354f1a9 100644
--- a/src/wallet/external_signer_scriptpubkeyman.cpp
+++ b/src/wallet/external_signer_scriptpubkeyman.cpp
@@ -79,7 +79,7 @@ util::Result<void> ExternalSignerScriptPubKeyMan::DisplayAddress(const CTxDestin
 }
 
 // If sign is true, transaction must previously have been filled
-std::optional<PSBTError> ExternalSignerScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
+std::optional<PSBTError> ExternalSignerScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
 {
     if (!sign) {
         return DescriptorScriptPubKeyMan::FillPSBT(psbt, txdata, sighash_type, false, bip32derivs, n_signed, finalize);
diff --git a/src/wallet/external_signer_scriptpubkeyman.h b/src/wallet/external_signer_scriptpubkeyman.h
index 10d67d2ab47..66c2dd9d170 100644
--- a/src/wallet/external_signer_scriptpubkeyman.h
+++ b/src/wallet/external_signer_scriptpubkeyman.h
@@ -35,7 +35,7 @@ class ExternalSignerScriptPubKeyMan : public DescriptorScriptPubKeyMan
   */
  util::Result<void> DisplayAddress(const CTxDestination& dest, const ExternalSigner& signer) const;
 
-  std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
+  std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type = std::nullopt, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
 };
 } // namespace wallet
 #endif // BITCOIN_WALLET_EXTERNAL_SIGNER_SCRIPTPUBKEYMAN_H
diff --git a/src/wallet/feebumper.cpp b/src/wallet/feebumper.cpp
index 0a58285a969..f4c8be938e2 100644
--- a/src/wallet/feebumper.cpp
+++ b/src/wallet/feebumper.cpp
@@ -338,8 +338,8 @@ bool SignTransaction(CWallet& wallet, CMutableTransaction& mtx) {
         // First fill transaction with our data without signing,
         // so external signers are not asked to sign more than once.
         bool complete;
-        wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, false /* sign */, true /* bip32derivs */);
-        auto err{wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, true /* sign */, false  /* bip32derivs */)};
+        wallet.FillPSBT(psbtx, complete, std::nullopt, /*sign=*/false, /*bip32derivs=*/true);
+        auto err{wallet.FillPSBT(psbtx, complete, std::nullopt, /*sign=*/true, /*bip32derivs=*/false)};
         if (err) return false;
         complete = FinalizeAndExtractPSBT(psbtx, mtx);
         return complete;
diff --git a/src/wallet/interfaces.cpp b/src/wallet/interfaces.cpp
index 5308b4418d7..0f8925f77ee 100644
--- a/src/wallet/interfaces.cpp
+++ b/src/wallet/interfaces.cpp
@@ -383,7 +383,7 @@ public:
         }
         return {};
     }
-    std::optional<PSBTError> fillPSBT(int sighash_type,
+    std::optional<PSBTError> fillPSBT(std::optional<int> sighash_type,
         bool sign,
         bool bip32derivs,
         size_t* n_signed,
diff --git a/src/wallet/rpc/spend.cpp b/src/wallet/rpc/spend.cpp
index a59d274b176..4626a02da32 100644
--- a/src/wallet/rpc/spend.cpp
+++ b/src/wallet/rpc/spend.cpp
@@ -100,8 +100,8 @@ static UniValue FinishTransaction(const std::shared_ptr<CWallet> pwallet, const
     // First fill transaction with our data without signing,
     // so external signers are not asked to sign more than once.
     bool complete;
-    pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, /*sign=*/false, /*bip32derivs=*/true);
-    const auto err{pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, /*sign=*/true, /*bip32derivs=*/false)};
+    pwallet->FillPSBT(psbtx, complete, std::nullopt, /*sign=*/false, /*bip32derivs=*/true);
+    const auto err{pwallet->FillPSBT(psbtx, complete, std::nullopt, /*sign=*/true, /*bip32derivs=*/false)};
     if (err) {
         throw JSONRPCPSBTError(*err);
     }
@@ -1175,7 +1175,7 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
     } else {
         PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
-        const auto err{pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, /*sign=*/false, /*bip32derivs=*/true)};
+        const auto err{pwallet->FillPSBT(psbtx, complete, std::nullopt, /*sign=*/false, /*bip32derivs=*/true)};
         CHECK_NONFATAL(!err);
         CHECK_NONFATAL(!complete);
         DataStream ssTx{};
@@ -1777,7 +1777,7 @@ RPCHelpMan walletcreatefundedpsbt()
     // Fill transaction with out data but don't sign
     bool bip32derivs = request.params[4].isNull() ? true : request.params[4].get_bool();
     bool complete = true;
-    const auto err{wallet.FillPSBT(psbtx, complete, 1, /*sign=*/false, /*bip32derivs=*/bip32derivs)};
+    const auto err{wallet.FillPSBT(psbtx, complete, std::nullopt, /*sign=*/false, /*bip32derivs=*/bip32derivs)};
     if (err) {
         throw JSONRPCPSBTError(*err);
     }
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index c9d52c18dff..0d20a73871b 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -1311,11 +1311,12 @@ SigningResult DescriptorScriptPubKeyMan::SignMessage(const std::string& message,
     return SigningResult::OK;
 }
 
-std::optional<PSBTError> DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, const PrecomputedTransactionData& txdata, int sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
+std::optional<PSBTError> DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type, bool sign, bool bip32derivs, int* n_signed, bool finalize) const
 {
     if (n_signed) {
         *n_signed = 0;
     }
+    if (!sighash_type) sighash_type = SIGHASH_DEFAULT;
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
         const CTxIn& txin = psbtx.tx->vin[i];
         PSBTInput& input = psbtx.inputs.at(i);
@@ -1386,7 +1387,7 @@ std::optional<PSBTError> DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTran
             }
         }
 
-        PSBTError res = SignPSBTInput(HidingSigningProvider(keys.get(), /*hide_secret=*/!sign, /*hide_origin=*/!bip32derivs), psbtx, i, &txdata, sighash_type, nullptr, finalize);
+        PSBTError res = SignPSBTInput(HidingSigningProvider(keys.get(), /*hide_secret=*/!sign, /*hide_origin=*/!bip32derivs), psbtx, i, &txdata, *sighash_type, nullptr, finalize);
         if (res != PSBTError::OK && res != PSBTError::INCOMPLETE) {
             return res;
         }
diff --git a/src/wallet/scriptpubkeyman.h b/src/wallet/scriptpubkeyman.h
index d8aac3ed02f..13b8233879c 100644
--- a/src/wallet/scriptpubkeyman.h
+++ b/src/wallet/scriptpubkeyman.h
@@ -153,7 +153,7 @@ public:
     /** Sign a message with the given script */
     virtual SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const { return SigningResult::SIGNING_FAILED; };
     /** Adds script and derivation path information to a PSBT, and optionally signs it. */
-    virtual std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const { return common::PSBTError::UNSUPPORTED; }
+    virtual std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type = std::nullopt, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const { return common::PSBTError::UNSUPPORTED; }
 
     virtual uint256 GetID() const { return uint256(); }
 
@@ -382,7 +382,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, bilingual_str>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
-    std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
+    std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, std::optional<int> sighash_type = std::nullopt, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
 
     uint256 GetID() const override;
 
diff --git a/src/wallet/test/fuzz/scriptpubkeyman.cpp b/src/wallet/test/fuzz/scriptpubkeyman.cpp
index 63768c89afc..6a1c51290b3 100644
--- a/src/wallet/test/fuzz/scriptpubkeyman.cpp
+++ b/src/wallet/test/fuzz/scriptpubkeyman.cpp
@@ -192,7 +192,8 @@ FUZZ_TARGET(scriptpubkeyman, .init = initialize_spkm)
                 }
                 auto psbt{*opt_psbt};
                 const PrecomputedTransactionData txdata{PrecomputePSBTData(psbt)};
-                const int sighash_type{fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 150)};
+                std::optional<int> sighash_type{fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 151)};
+                if (sighash_type == 151) sighash_type = std::nullopt;
                 auto sign  = fuzzed_data_provider.ConsumeBool();
                 auto bip32derivs = fuzzed_data_provider.ConsumeBool();
                 auto finalize = fuzzed_data_provider.ConsumeBool();
diff --git a/src/wallet/test/psbt_wallet_tests.cpp b/src/wallet/test/psbt_wallet_tests.cpp
index c44ea496339..63153fb55db 100644
--- a/src/wallet/test/psbt_wallet_tests.cpp
+++ b/src/wallet/test/psbt_wallet_tests.cpp
@@ -65,7 +65,7 @@ BOOST_AUTO_TEST_CASE(psbt_updater_test)
 
     // Fill transaction with our data
     bool complete = true;
-    BOOST_REQUIRE(!m_wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, false, true));
+    BOOST_REQUIRE(!m_wallet.FillPSBT(psbtx, complete, std::nullopt, false, true));
 
     // Get the final tx
     DataStream ssTx{};
@@ -78,7 +78,7 @@ BOOST_AUTO_TEST_CASE(psbt_updater_test)
 
     // Try to sign the mutated input
     SignatureData sigdata;
-    BOOST_CHECK(m_wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, true, true));
+    BOOST_CHECK(m_wallet.FillPSBT(psbtx, complete, std::nullopt, true, true));
 }
 
 BOOST_AUTO_TEST_CASE(parse_hd_keypath)
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 3c5df177679..215d7b505cd 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2101,11 +2101,12 @@ bool CWallet::SignTransaction(CMutableTransaction& tx, const std::map<COutPoint,
     return false;
 }
 
-std::optional<PSBTError> CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& complete, int sighash_type, bool sign, bool bip32derivs, size_t * n_signed, bool finalize) const
+std::optional<PSBTError> CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& complete, std::optional<int> sighash_type, bool sign, bool bip32derivs, size_t * n_signed, bool finalize) const
 {
     if (n_signed) {
         *n_signed = 0;
     }
+    if (!sighash_type) sighash_type = SIGHASH_DEFAULT;
     LOCK(cs_wallet);
     // Get all of the previous transactions
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
@@ -2144,7 +2145,7 @@ std::optional<PSBTError> CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bo
         }
     }
 
-    RemoveUnnecessaryTransactions(psbtx, sighash_type);
+    RemoveUnnecessaryTransactions(psbtx, *sighash_type);
 
     // Complete if every input is now signed
     complete = true;
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index e32b8c7272b..c6b56bd9ef0 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -659,7 +659,7 @@ public:
      */
     std::optional<common::PSBTError> FillPSBT(PartiallySignedTransaction& psbtx,
                   bool& complete,
-                  int sighash_type = SIGHASH_DEFAULT,
+                  std::optional<int> sighash_type = std::nullopt,
                   bool sign = true,
                   bool bip32derivs = true,
                   size_t* n_signed = nullptr,