17 files changed, 222 insertions, 223 deletions
diff --git a/contrib/verify-commits/README.md b/contrib/verify-commits/README.md
index 27ca15acb4..1215962a16 100644
--- a/contrib/verify-commits/README.md
+++ b/contrib/verify-commits/README.md
@@ -37,7 +37,8 @@ Configuration files
 
 Import trusted keys
 -------------------
-In order to check the commit signatures you must add the trusted PGP keys to your machine. This can be done in Linux by running
+In order to check the commit signatures, you must add the trusted PGP keys to your machine. [GnuPG](https://gnupg.org/) may be used to import the trusted keys by running the following command:
+
 ```sh
 gpg --recv-keys $(<contrib/verify-commits/trusted-keys)
 ```
diff --git a/src/init.cpp b/src/init.cpp
index 9ba9b2803a..8876b54fde 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -380,7 +380,7 @@ void SetupServerArgs()
     gArgs.AddArg("-conf=<file>", strprintf("Specify configuration file. Relative paths will be prefixed by datadir location. (default: %s)", BITCOIN_CONF_FILENAME), false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-datadir=<dir>", "Specify data directory", false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-dbbatchsize", strprintf("Maximum database write batch size in bytes (default: %u)", nDefaultDbBatchSize), true, OptionsCategory::OPTIONS);
-    gArgs.AddArg("-dbcache=<n>", strprintf("Set database cache size in MiB (%d to %d, default: %d)", nMinDbCache, nMaxDbCache, nDefaultDbCache), false, OptionsCategory::OPTIONS);
+    gArgs.AddArg("-dbcache=<n>", strprintf("Maximum database cache size <n> MiB (%d to %d, default: %d). In addition, unused mempool memory is shared for this cache (see -maxmempool).", nMinDbCache, nMaxDbCache, nDefaultDbCache), false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-debuglogfile=<file>", strprintf("Specify location of debug log file. Relative paths will be prefixed by a net-specific datadir location. (-nodebuglogfile to disable; default: %s)", DEFAULT_DEBUGLOGFILE), false, OptionsCategory::OPTIONS);
     gArgs.AddArg("-feefilter", strprintf("Tell other nodes to filter invs to us by our mempool min fee (default: %u)", DEFAULT_FEEFILTER), true, OptionsCategory::OPTIONS);
     gArgs.AddArg("-includeconf=<file>", "Specify additional configuration file, relative to the -datadir path (only useable from configuration file, not command line)", false, OptionsCategory::OPTIONS);
diff --git a/src/interfaces/wallet.cpp b/src/interfaces/wallet.cpp
index 5b5430037c..0dac75834e 100644
--- a/src/interfaces/wallet.cpp
+++ b/src/interfaces/wallet.cpp
@@ -135,55 +135,55 @@ WalletTxOut MakeWalletTxOut(interfaces::Chain::Lock& locked_chain,
 class WalletImpl : public Wallet
 {
 public:
-    explicit WalletImpl(const std::shared_ptr<CWallet>& wallet) : m_shared_wallet(wallet), m_wallet(*wallet.get()) {}
+    explicit WalletImpl(const std::shared_ptr<CWallet>& wallet) : m_wallet(wallet) {}
 
     bool encryptWallet(const SecureString& wallet_passphrase) override
     {
-        return m_wallet.EncryptWallet(wallet_passphrase);
+        return m_wallet->EncryptWallet(wallet_passphrase);
     }
-    bool isCrypted() override { return m_wallet.IsCrypted(); }
-    bool lock() override { return m_wallet.Lock(); }
-    bool unlock(const SecureString& wallet_passphrase) override { return m_wallet.Unlock(wallet_passphrase); }
-    bool isLocked() override { return m_wallet.IsLocked(); }
+    bool isCrypted() override { return m_wallet->IsCrypted(); }
+    bool lock() override { return m_wallet->Lock(); }
+    bool unlock(const SecureString& wallet_passphrase) override { return m_wallet->Unlock(wallet_passphrase); }
+    bool isLocked() override { return m_wallet->IsLocked(); }
     bool changeWalletPassphrase(const SecureString& old_wallet_passphrase,
         const SecureString& new_wallet_passphrase) override
     {
-        return m_wallet.ChangeWalletPassphrase(old_wallet_passphrase, new_wallet_passphrase);
+        return m_wallet->ChangeWalletPassphrase(old_wallet_passphrase, new_wallet_passphrase);
     }
-    void abortRescan() override { m_wallet.AbortRescan(); }
-    bool backupWallet(const std::string& filename) override { return m_wallet.BackupWallet(filename); }
-    std::string getWalletName() override { return m_wallet.GetName(); }
+    void abortRescan() override { m_wallet->AbortRescan(); }
+    bool backupWallet(const std::string& filename) override { return m_wallet->BackupWallet(filename); }
+    std::string getWalletName() override { return m_wallet->GetName(); }
     bool getKeyFromPool(bool internal, CPubKey& pub_key) override
     {
-        return m_wallet.GetKeyFromPool(pub_key, internal);
+        return m_wallet->GetKeyFromPool(pub_key, internal);
     }
-    bool getPubKey(const CKeyID& address, CPubKey& pub_key) override { return m_wallet.GetPubKey(address, pub_key); }
-    bool getPrivKey(const CKeyID& address, CKey& key) override { return m_wallet.GetKey(address, key); }
-    bool isSpendable(const CTxDestination& dest) override { return IsMine(m_wallet, dest) & ISMINE_SPENDABLE; }
-    bool haveWatchOnly() override { return m_wallet.HaveWatchOnly(); };
+    bool getPubKey(const CKeyID& address, CPubKey& pub_key) override { return m_wallet->GetPubKey(address, pub_key); }
+    bool getPrivKey(const CKeyID& address, CKey& key) override { return m_wallet->GetKey(address, key); }
+    bool isSpendable(const CTxDestination& dest) override { return IsMine(*m_wallet, dest) & ISMINE_SPENDABLE; }
+    bool haveWatchOnly() override { return m_wallet->HaveWatchOnly(); };
     bool setAddressBook(const CTxDestination& dest, const std::string& name, const std::string& purpose) override
     {
-        return m_wallet.SetAddressBook(dest, name, purpose);
+        return m_wallet->SetAddressBook(dest, name, purpose);
     }
     bool delAddressBook(const CTxDestination& dest) override
     {
-        return m_wallet.DelAddressBook(dest);
+        return m_wallet->DelAddressBook(dest);
     }
     bool getAddress(const CTxDestination& dest,
         std::string* name,
         isminetype* is_mine,
         std::string* purpose) override
     {
-        LOCK(m_wallet.cs_wallet);
-        auto it = m_wallet.mapAddressBook.find(dest);
-        if (it == m_wallet.mapAddressBook.end()) {
+        LOCK(m_wallet->cs_wallet);
+        auto it = m_wallet->mapAddressBook.find(dest);
+        if (it == m_wallet->mapAddressBook.end()) {
             return false;
         }
         if (name) {
             *name = it->second.name;
         }
         if (is_mine) {
-            *is_mine = IsMine(m_wallet, dest);
+            *is_mine = IsMine(*m_wallet, dest);
         }
         if (purpose) {
             *purpose = it->second.purpose;
@@ -192,52 +192,52 @@ public:
     }
     std::vector<WalletAddress> getAddresses() override
     {
-        LOCK(m_wallet.cs_wallet);
+        LOCK(m_wallet->cs_wallet);
         std::vector<WalletAddress> result;
-        for (const auto& item : m_wallet.mapAddressBook) {
-            result.emplace_back(item.first, IsMine(m_wallet, item.first), item.second.name, item.second.purpose);
+        for (const auto& item : m_wallet->mapAddressBook) {
+            result.emplace_back(item.first, IsMine(*m_wallet, item.first), item.second.name, item.second.purpose);
         }
         return result;
     }
-    void learnRelatedScripts(const CPubKey& key, OutputType type) override { m_wallet.LearnRelatedScripts(key, type); }
+    void learnRelatedScripts(const CPubKey& key, OutputType type) override { m_wallet->LearnRelatedScripts(key, type); }
     bool addDestData(const CTxDestination& dest, const std::string& key, const std::string& value) override
     {
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.AddDestData(dest, key, value);
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->AddDestData(dest, key, value);
     }
     bool eraseDestData(const CTxDestination& dest, const std::string& key) override
     {
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.EraseDestData(dest, key);
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->EraseDestData(dest, key);
     }
     std::vector<std::string> getDestValues(const std::string& prefix) override
     {
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.GetDestValues(prefix);
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->GetDestValues(prefix);
     }
     void lockCoin(const COutPoint& output) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.LockCoin(output);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->LockCoin(output);
     }
     void unlockCoin(const COutPoint& output) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.UnlockCoin(output);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->UnlockCoin(output);
     }
     bool isLockedCoin(const COutPoint& output) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.IsLockedCoin(output.hash, output.n);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->IsLockedCoin(output.hash, output.n);
     }
     void listLockedCoins(std::vector<COutPoint>& outputs) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.ListLockedCoins(outputs);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->ListLockedCoins(outputs);
     }
     std::unique_ptr<PendingWalletTx> createTransaction(const std::vector<CRecipient>& recipients,
         const CCoinControl& coin_control,
@@ -246,25 +246,25 @@ public:
         CAmount& fee,
         std::string& fail_reason) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        auto pending = MakeUnique<PendingWalletTxImpl>(m_wallet);
-        if (!m_wallet.CreateTransaction(*locked_chain, recipients, pending->m_tx, pending->m_key, fee, change_pos,
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        auto pending = MakeUnique<PendingWalletTxImpl>(*m_wallet);
+        if (!m_wallet->CreateTransaction(*locked_chain, recipients, pending->m_tx, pending->m_key, fee, change_pos,
                 fail_reason, coin_control, sign)) {
             return {};
         }
         return std::move(pending);
     }
-    bool transactionCanBeAbandoned(const uint256& txid) override { return m_wallet.TransactionCanBeAbandoned(txid); }
+    bool transactionCanBeAbandoned(const uint256& txid) override { return m_wallet->TransactionCanBeAbandoned(txid); }
     bool abandonTransaction(const uint256& txid) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.AbandonTransaction(*locked_chain, txid);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->AbandonTransaction(*locked_chain, txid);
     }
     bool transactionCanBeBumped(const uint256& txid) override
     {
-        return feebumper::TransactionCanBeBumped(&m_wallet, txid);
+        return feebumper::TransactionCanBeBumped(m_wallet.get(), txid);
     }
     bool createBumpTransaction(const uint256& txid,
         const CCoinControl& coin_control,
@@ -274,46 +274,46 @@ public:
         CAmount& new_fee,
         CMutableTransaction& mtx) override
     {
-        return feebumper::CreateTransaction(&m_wallet, txid, coin_control, total_fee, errors, old_fee, new_fee, mtx) ==
+        return feebumper::CreateTransaction(m_wallet.get(), txid, coin_control, total_fee, errors, old_fee, new_fee, mtx) ==
                feebumper::Result::OK;
     }
-    bool signBumpTransaction(CMutableTransaction& mtx) override { return feebumper::SignTransaction(&m_wallet, mtx); }
+    bool signBumpTransaction(CMutableTransaction& mtx) override { return feebumper::SignTransaction(m_wallet.get(), mtx); }
     bool commitBumpTransaction(const uint256& txid,
         CMutableTransaction&& mtx,
         std::vector<std::string>& errors,
         uint256& bumped_txid) override
     {
-        return feebumper::CommitTransaction(&m_wallet, txid, std::move(mtx), errors, bumped_txid) ==
+        return feebumper::CommitTransaction(m_wallet.get(), txid, std::move(mtx), errors, bumped_txid) ==
                feebumper::Result::OK;
     }
     CTransactionRef getTx(const uint256& txid) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        auto mi = m_wallet.mapWallet.find(txid);
-        if (mi != m_wallet.mapWallet.end()) {
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        auto mi = m_wallet->mapWallet.find(txid);
+        if (mi != m_wallet->mapWallet.end()) {
             return mi->second.tx;
         }
         return {};
     }
     WalletTx getWalletTx(const uint256& txid) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        auto mi = m_wallet.mapWallet.find(txid);
-        if (mi != m_wallet.mapWallet.end()) {
-            return MakeWalletTx(*locked_chain, m_wallet, mi->second);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        auto mi = m_wallet->mapWallet.find(txid);
+        if (mi != m_wallet->mapWallet.end()) {
+            return MakeWalletTx(*locked_chain, *m_wallet, mi->second);
         }
         return {};
     }
     std::vector<WalletTx> getWalletTxs() override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
         std::vector<WalletTx> result;
-        result.reserve(m_wallet.mapWallet.size());
-        for (const auto& entry : m_wallet.mapWallet) {
-            result.emplace_back(MakeWalletTx(*locked_chain, m_wallet, entry.second));
+        result.reserve(m_wallet->mapWallet.size());
+        for (const auto& entry : m_wallet->mapWallet) {
+            result.emplace_back(MakeWalletTx(*locked_chain, *m_wallet, entry.second));
         }
         return result;
     }
@@ -322,16 +322,16 @@ public:
         int& num_blocks,
         int64_t& block_time) override
     {
-        auto locked_chain = m_wallet.chain().lock(true /* try_lock */);
+        auto locked_chain = m_wallet->chain().lock(true /* try_lock */);
         if (!locked_chain) {
             return false;
         }
-        TRY_LOCK(m_wallet.cs_wallet, locked_wallet);
+        TRY_LOCK(m_wallet->cs_wallet, locked_wallet);
         if (!locked_wallet) {
             return false;
         }
-        auto mi = m_wallet.mapWallet.find(txid);
-        if (mi == m_wallet.mapWallet.end()) {
+        auto mi = m_wallet->mapWallet.find(txid);
+        if (mi == m_wallet->mapWallet.end()) {
             return false;
         }
         if (Optional<int> height = locked_chain->getHeight()) {
@@ -350,37 +350,37 @@ public:
         bool& in_mempool,
         int& num_blocks) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        auto mi = m_wallet.mapWallet.find(txid);
-        if (mi != m_wallet.mapWallet.end()) {
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        auto mi = m_wallet->mapWallet.find(txid);
+        if (mi != m_wallet->mapWallet.end()) {
             num_blocks = locked_chain->getHeight().get_value_or(-1);
             in_mempool = mi->second.InMempool();
             order_form = mi->second.vOrderForm;
             tx_status = MakeWalletTxStatus(*locked_chain, mi->second);
-            return MakeWalletTx(*locked_chain, m_wallet, mi->second);
+            return MakeWalletTx(*locked_chain, *m_wallet, mi->second);
         }
         return {};
     }
     WalletBalances getBalances() override
     {
         WalletBalances result;
-        result.balance = m_wallet.GetBalance();
-        result.unconfirmed_balance = m_wallet.GetUnconfirmedBalance();
-        result.immature_balance = m_wallet.GetImmatureBalance();
-        result.have_watch_only = m_wallet.HaveWatchOnly();
+        result.balance = m_wallet->GetBalance();
+        result.unconfirmed_balance = m_wallet->GetUnconfirmedBalance();
+        result.immature_balance = m_wallet->GetImmatureBalance();
+        result.have_watch_only = m_wallet->HaveWatchOnly();
         if (result.have_watch_only) {
-            result.watch_only_balance = m_wallet.GetBalance(ISMINE_WATCH_ONLY);
-            result.unconfirmed_watch_only_balance = m_wallet.GetUnconfirmedWatchOnlyBalance();
-            result.immature_watch_only_balance = m_wallet.GetImmatureWatchOnlyBalance();
+            result.watch_only_balance = m_wallet->GetBalance(ISMINE_WATCH_ONLY);
+            result.unconfirmed_watch_only_balance = m_wallet->GetUnconfirmedWatchOnlyBalance();
+            result.immature_watch_only_balance = m_wallet->GetImmatureWatchOnlyBalance();
         }
         return result;
     }
     bool tryGetBalances(WalletBalances& balances, int& num_blocks) override
     {
-        auto locked_chain = m_wallet.chain().lock(true /* try_lock */);
+        auto locked_chain = m_wallet->chain().lock(true /* try_lock */);
         if (!locked_chain) return false;
-        TRY_LOCK(m_wallet.cs_wallet, locked_wallet);
+        TRY_LOCK(m_wallet->cs_wallet, locked_wallet);
         if (!locked_wallet) {
             return false;
         }
@@ -388,68 +388,68 @@ public:
         num_blocks = locked_chain->getHeight().get_value_or(-1);
         return true;
     }
-    CAmount getBalance() override { return m_wallet.GetBalance(); }
+    CAmount getBalance() override { return m_wallet->GetBalance(); }
     CAmount getAvailableBalance(const CCoinControl& coin_control) override
     {
-        return m_wallet.GetAvailableBalance(&coin_control);
+        return m_wallet->GetAvailableBalance(&coin_control);
     }
     isminetype txinIsMine(const CTxIn& txin) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.IsMine(txin);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->IsMine(txin);
     }
     isminetype txoutIsMine(const CTxOut& txout) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.IsMine(txout);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->IsMine(txout);
     }
     CAmount getDebit(const CTxIn& txin, isminefilter filter) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.GetDebit(txin, filter);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->GetDebit(txin, filter);
     }
     CAmount getCredit(const CTxOut& txout, isminefilter filter) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
-        return m_wallet.GetCredit(txout, filter);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
+        return m_wallet->GetCredit(txout, filter);
     }
     CoinsList listCoins() override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
         CoinsList result;
-        for (const auto& entry : m_wallet.ListCoins(*locked_chain)) {
+        for (const auto& entry : m_wallet->ListCoins(*locked_chain)) {
             auto& group = result[entry.first];
             for (const auto& coin : entry.second) {
                 group.emplace_back(COutPoint(coin.tx->GetHash(), coin.i),
-                    MakeWalletTxOut(*locked_chain, m_wallet, *coin.tx, coin.i, coin.nDepth));
+                    MakeWalletTxOut(*locked_chain, *m_wallet, *coin.tx, coin.i, coin.nDepth));
             }
         }
         return result;
     }
     std::vector<WalletTxOut> getCoins(const std::vector<COutPoint>& outputs) override
     {
-        auto locked_chain = m_wallet.chain().lock();
-        LOCK(m_wallet.cs_wallet);
+        auto locked_chain = m_wallet->chain().lock();
+        LOCK(m_wallet->cs_wallet);
         std::vector<WalletTxOut> result;
         result.reserve(outputs.size());
         for (const auto& output : outputs) {
             result.emplace_back();
-            auto it = m_wallet.mapWallet.find(output.hash);
-            if (it != m_wallet.mapWallet.end()) {
+            auto it = m_wallet->mapWallet.find(output.hash);
+            if (it != m_wallet->mapWallet.end()) {
                 int depth = it->second.GetDepthInMainChain(*locked_chain);
                 if (depth >= 0) {
-                    result.back() = MakeWalletTxOut(*locked_chain, m_wallet, it->second, output.n, depth);
+                    result.back() = MakeWalletTxOut(*locked_chain, *m_wallet, it->second, output.n, depth);
                 }
             }
         }
         return result;
     }
-    CAmount getRequiredFee(unsigned int tx_bytes) override { return GetRequiredFee(m_wallet, tx_bytes); }
+    CAmount getRequiredFee(unsigned int tx_bytes) override { return GetRequiredFee(*m_wallet, tx_bytes); }
     CAmount getMinimumFee(unsigned int tx_bytes,
         const CCoinControl& coin_control,
         int* returned_target,
@@ -457,55 +457,54 @@ public:
     {
         FeeCalculation fee_calc;
         CAmount result;
-        result = GetMinimumFee(m_wallet, tx_bytes, coin_control, ::mempool, ::feeEstimator, &fee_calc);
+        result = GetMinimumFee(*m_wallet, tx_bytes, coin_control, ::mempool, ::feeEstimator, &fee_calc);
         if (returned_target) *returned_target = fee_calc.returnedTarget;
         if (reason) *reason = fee_calc.reason;
         return result;
     }
-    unsigned int getConfirmTarget() override { return m_wallet.m_confirm_target; }
-    bool hdEnabled() override { return m_wallet.IsHDEnabled(); }
-    bool canGetAddresses() override { return m_wallet.CanGetAddresses(); }
-    bool IsWalletFlagSet(uint64_t flag) override { return m_wallet.IsWalletFlagSet(flag); }
-    OutputType getDefaultAddressType() override { return m_wallet.m_default_address_type; }
-    OutputType getDefaultChangeType() override { return m_wallet.m_default_change_type; }
+    unsigned int getConfirmTarget() override { return m_wallet->m_confirm_target; }
+    bool hdEnabled() override { return m_wallet->IsHDEnabled(); }
+    bool canGetAddresses() override { return m_wallet->CanGetAddresses(); }
+    bool IsWalletFlagSet(uint64_t flag) override { return m_wallet->IsWalletFlagSet(flag); }
+    OutputType getDefaultAddressType() override { return m_wallet->m_default_address_type; }
+    OutputType getDefaultChangeType() override { return m_wallet->m_default_change_type; }
     void remove() override
     {
-        RemoveWallet(m_shared_wallet);
+        RemoveWallet(m_wallet);
     }
     std::unique_ptr<Handler> handleUnload(UnloadFn fn) override
     {
-        return MakeHandler(m_wallet.NotifyUnload.connect(fn));
+        return MakeHandler(m_wallet->NotifyUnload.connect(fn));
     }
     std::unique_ptr<Handler> handleShowProgress(ShowProgressFn fn) override
     {
-        return MakeHandler(m_wallet.ShowProgress.connect(fn));
+        return MakeHandler(m_wallet->ShowProgress.connect(fn));
     }
     std::unique_ptr<Handler> handleStatusChanged(StatusChangedFn fn) override
     {
-        return MakeHandler(m_wallet.NotifyStatusChanged.connect([fn](CCryptoKeyStore*) { fn(); }));
+        return MakeHandler(m_wallet->NotifyStatusChanged.connect([fn](CCryptoKeyStore*) { fn(); }));
     }
     std::unique_ptr<Handler> handleAddressBookChanged(AddressBookChangedFn fn) override
     {
-        return MakeHandler(m_wallet.NotifyAddressBookChanged.connect(
+        return MakeHandler(m_wallet->NotifyAddressBookChanged.connect(
             [fn](CWallet*, const CTxDestination& address, const std::string& label, bool is_mine,
                 const std::string& purpose, ChangeType status) { fn(address, label, is_mine, purpose, status); }));
     }
     std::unique_ptr<Handler> handleTransactionChanged(TransactionChangedFn fn) override
     {
-        return MakeHandler(m_wallet.NotifyTransactionChanged.connect(
+        return MakeHandler(m_wallet->NotifyTransactionChanged.connect(
             [fn](CWallet*, const uint256& txid, ChangeType status) { fn(txid, status); }));
     }
     std::unique_ptr<Handler> handleWatchOnlyChanged(WatchOnlyChangedFn fn) override
     {
-        return MakeHandler(m_wallet.NotifyWatchonlyChanged.connect(fn));
+        return MakeHandler(m_wallet->NotifyWatchonlyChanged.connect(fn));
     }
     std::unique_ptr<Handler> handleCanGetAddressesChanged(CanGetAddressesChangedFn fn) override
     {
-        return MakeHandler(m_wallet.NotifyCanGetAddressesChanged.connect(fn));
+        return MakeHandler(m_wallet->NotifyCanGetAddressesChanged.connect(fn));
     }
 
-    std::shared_ptr<CWallet> m_shared_wallet;
-    CWallet& m_wallet;
+    std::shared_ptr<CWallet> m_wallet;
 };
 
 class WalletClientImpl : public ChainClient
diff --git a/src/node/transaction.cpp b/src/node/transaction.cpp
index c9cdd0d1cd..7b9b4310e7 100644
--- a/src/node/transaction.cpp
+++ b/src/node/transaction.cpp
@@ -12,7 +12,7 @@
 
 #include <future>
 
-const char* TransactionErrorString(const TransactionError err)
+std::string TransactionErrorString(const TransactionError err)
 {
     switch (err) {
         case TransactionError::OK:
@@ -33,22 +33,16 @@ const char* TransactionErrorString(const TransactionError err)
             return "PSBTs not compatible (different transactions)";
         case TransactionError::SIGHASH_MISMATCH:
             return "Specified sighash value does not match existing value";
-
-        case TransactionError::UNKNOWN_ERROR:
-        default: break;
+        // no default case, so the compiler can warn about missing cases
     }
-    return "Unknown error";
+    assert(false);
 }
 
-bool BroadcastTransaction(const CTransactionRef tx, uint256& hashTx, TransactionError& error, std::string& err_string, const bool allowhighfees)
+TransactionError BroadcastTransaction(const CTransactionRef tx, uint256& hashTx, std::string& err_string, const CAmount& highfee)
 {
     std::promise<void> promise;
     hashTx = tx->GetHash();
 
-    CAmount nMaxRawTxFee = maxTxFee;
-    if (allowhighfees)
-        nMaxRawTxFee = 0;
-
     { // cs_main scope
     LOCK(cs_main);
     CCoinsViewCache &view = *pcoinsTip;
@@ -63,19 +57,16 @@ bool BroadcastTransaction(const CTransactionRef tx, uint256& hashTx, Transaction
         CValidationState state;
         bool fMissingInputs;
         if (!AcceptToMemoryPool(mempool, state, std::move(tx), &fMissingInputs,
-                                nullptr /* plTxnReplaced */, false /* bypass_limits */, nMaxRawTxFee)) {
+                                nullptr /* plTxnReplaced */, false /* bypass_limits */, highfee)) {
             if (state.IsInvalid()) {
                 err_string = FormatStateMessage(state);
-                error = TransactionError::MEMPOOL_REJECTED;
-                return false;
+                return TransactionError::MEMPOOL_REJECTED;
             } else {
                 if (fMissingInputs) {
-                    error = TransactionError::MISSING_INPUTS;
-                    return false;
+                    return TransactionError::MISSING_INPUTS;
                 }
                 err_string = FormatStateMessage(state);
-                error = TransactionError::MEMPOOL_ERROR;
-                return false;
+                return TransactionError::MEMPOOL_ERROR;
             }
         } else {
             // If wallet is enabled, ensure that the wallet has been made aware
@@ -88,8 +79,7 @@ bool BroadcastTransaction(const CTransactionRef tx, uint256& hashTx, Transaction
             });
         }
     } else if (fHaveChain) {
-        error = TransactionError::ALREADY_IN_CHAIN;
-        return false;
+        return TransactionError::ALREADY_IN_CHAIN;
     } else {
         // Make sure we don't block forever if re-sending
         // a transaction already in mempool.
@@ -100,16 +90,14 @@ bool BroadcastTransaction(const CTransactionRef tx, uint256& hashTx, Transaction
 
     promise.get_future().wait();
 
-    if(!g_connman) {
-        error = TransactionError::P2P_DISABLED;
-        return false;
+    if (!g_connman) {
+        return TransactionError::P2P_DISABLED;
     }
 
     CInv inv(MSG_TX, hashTx);
-    g_connman->ForEachNode([&inv](CNode* pnode)
-    {
+    g_connman->ForEachNode([&inv](CNode* pnode) {
         pnode->PushInventory(inv);
     });
 
-    return true;
-    }
+    return TransactionError::OK;
+}
diff --git a/src/node/transaction.h b/src/node/transaction.h
index 3b0cbba98b..3457ececa4 100644
--- a/src/node/transaction.h
+++ b/src/node/transaction.h
@@ -1,17 +1,16 @@
-// Copyright (c) 2017-2018 The Bitcoin Core developers
+// Copyright (c) 2017-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_NODE_TRANSACTION_H
 #define BITCOIN_NODE_TRANSACTION_H
 
+#include <attributes.h>
 #include <primitives/transaction.h>
 #include <uint256.h>
 
 enum class TransactionError {
-    OK = 0,
-    UNKNOWN_ERROR,
-
+    OK, //!< No error
     MISSING_INPUTS,
     ALREADY_IN_CHAIN,
     P2P_DISABLED,
@@ -20,24 +19,19 @@ enum class TransactionError {
     INVALID_PSBT,
     PSBT_MISMATCH,
     SIGHASH_MISMATCH,
-
-    ERROR_COUNT
 };
 
-#define TRANSACTION_ERR_LAST TransactionError::ERROR_COUNT
-
-const char* TransactionErrorString(const TransactionError error);
+std::string TransactionErrorString(const TransactionError error);
 
 /**
  * Broadcast a transaction
  *
  * @param[in]  tx the transaction to broadcast
  * @param[out] &txid the txid of the transaction, if successfully broadcast
- * @param[out] &error reference to UniValue to fill with error info on failure
  * @param[out] &err_string reference to std::string to fill with error string if available
- * @param[in]  allowhighfees whether to allow fees exceeding maxTxFee
- * return true on success, false on error (and fills in `error`)
+ * @param[in]  highfee Reject txs with fees higher than this (if 0, accept any fee)
+ * return error
  */
-bool BroadcastTransaction(CTransactionRef tx, uint256& txid, TransactionError& error, std::string& err_string, bool allowhighfees = false);
+NODISCARD TransactionError BroadcastTransaction(CTransactionRef tx, uint256& txid, std::string& err_string, const CAmount& highfee);
 
 #endif // BITCOIN_NODE_TRANSACTION_H
diff --git a/src/psbt.cpp b/src/psbt.cpp
index 32fb459dec..0fb7d49d7d 100644
--- a/src/psbt.cpp
+++ b/src/psbt.cpp
@@ -309,21 +309,19 @@ bool FinalizeAndExtractPSBT(PartiallySignedTransaction& psbtx, CMutableTransacti
     return true;
 }
 
-bool CombinePSBTs(PartiallySignedTransaction& out, TransactionError& error, const std::vector<PartiallySignedTransaction>& psbtxs)
+TransactionError CombinePSBTs(PartiallySignedTransaction& out, const std::vector<PartiallySignedTransaction>& psbtxs)
 {
     out = psbtxs[0]; // Copy the first one
 
     // Merge
     for (auto it = std::next(psbtxs.begin()); it != psbtxs.end(); ++it) {
         if (!out.Merge(*it)) {
-            error = TransactionError::PSBT_MISMATCH;
-            return false;
+            return TransactionError::PSBT_MISMATCH;
         }
     }
     if (!out.IsSane()) {
-        error = TransactionError::INVALID_PSBT;
-        return false;
+        return TransactionError::INVALID_PSBT;
     }
 
-    return true;
+    return TransactionError::OK;
 }
diff --git a/src/psbt.h b/src/psbt.h
index 27b0aedd05..c889dad361 100644
--- a/src/psbt.h
+++ b/src/psbt.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Copyright (c) 2009-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -575,10 +575,9 @@ bool FinalizeAndExtractPSBT(PartiallySignedTransaction& psbtx, CMutableTransacti
  * Combines PSBTs with the same underlying transaction, resulting in a single PSBT with all partial signatures from each input.
  *
  * @param[out] &out   the combined PSBT, if successful
- * @param[out] &error reference to TransactionError to fill with error info on failure
  * @param[in]  psbtxs the PSBTs to combine
- * @return True if we successfully combined the transactions, false if they were not compatible
+ * @return error (OK if we successfully combined the transactions, other error if they were not compatible)
  */
-bool CombinePSBTs(PartiallySignedTransaction& out, TransactionError& error, const std::vector<PartiallySignedTransaction>& psbtxs);
+NODISCARD TransactionError CombinePSBTs(PartiallySignedTransaction& out, const std::vector<PartiallySignedTransaction>& psbtxs);
 
 #endif // BITCOIN_PSBT_H
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 7fb9ff2eaf..c73a8d48cf 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1,5 +1,5 @@
 // Copyright (c) 2010 Satoshi Nakamoto
-// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Copyright (c) 2009-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -1778,9 +1778,7 @@ static constexpr size_t PER_UTXO_OVERHEAD = sizeof(COutPoint) + sizeof(uint32_t)
 
 static UniValue getblockstats(const JSONRPCRequest& request)
 {
-    if (request.fHelp || request.params.size() < 1 || request.params.size() > 4) {
-        throw std::runtime_error(
-            RPCHelpMan{"getblockstats",
+    const RPCHelpMan help{"getblockstats",
                 "\nCompute per block statistics for a given window. All amounts are in satoshis.\n"
                 "It won't work for some heights with pruning.\n"
                 "It won't work without -txindex for utxo_size_inc, *fee or *feerate stats.\n",
@@ -1836,7 +1834,9 @@ static UniValue getblockstats(const JSONRPCRequest& request)
                     HelpExampleCli("getblockstats", "1000 '[\"minfeerate\",\"avgfeerate\"]'")
             + HelpExampleRpc("getblockstats", "1000 '[\"minfeerate\",\"avgfeerate\"]'")
                 },
-            }.ToString());
+    };
+    if (request.fHelp || !help.IsValidNumArgs(request.params.size())) {
+        throw std::runtime_error(help.ToString());
     }
 
     LOCK(cs_main);
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index 6bbbbc9876..c7b3478f44 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -523,13 +523,7 @@ static UniValue getnetworkinfo(const JSONRPCRequest& request)
 
 static UniValue setban(const JSONRPCRequest& request)
 {
-    std::string strCommand;
-    if (!request.params[1].isNull())
-        strCommand = request.params[1].get_str();
-    if (request.fHelp || request.params.size() < 2 ||
-        (strCommand != "add" && strCommand != "remove"))
-        throw std::runtime_error(
-            RPCHelpMan{"setban",
+    const RPCHelpMan help{"setban",
                 "\nAttempts to add or remove an IP/Subnet from the banned list.\n",
                 {
                     {"subnet", RPCArg::Type::STR, RPCArg::Optional::NO, "The IP/Subnet (see getpeerinfo for nodes IP) with an optional netmask (default is /32 = single IP)"},
@@ -543,7 +537,13 @@ static UniValue setban(const JSONRPCRequest& request)
                             + HelpExampleCli("setban", "\"192.168.0.0/24\" \"add\"")
                             + HelpExampleRpc("setban", "\"192.168.0.6\", \"add\", 86400")
                 },
-            }.ToString());
+    };
+    std::string strCommand;
+    if (!request.params[1].isNull())
+        strCommand = request.params[1].get_str();
+    if (request.fHelp || !help.IsValidNumArgs(request.params.size()) || (strCommand != "add" && strCommand != "remove")) {
+        throw std::runtime_error(help.ToString());
+    }
     if (!g_banman) {
         throw JSONRPCError(RPC_DATABASE_ERROR, "Error: Ban database not loaded");
     }
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 38e2dc237e..5a714a137e 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -1065,10 +1065,11 @@ static UniValue sendrawtransaction(const JSONRPCRequest& request)
 
     bool allowhighfees = false;
     if (!request.params[1].isNull()) allowhighfees = request.params[1].get_bool();
+    const CAmount highfee{allowhighfees ? 0 : ::maxTxFee};
     uint256 txid;
-    TransactionError err;
     std::string err_string;
-    if (!BroadcastTransaction(tx, txid, err, err_string, allowhighfees)) {
+    const TransactionError err = BroadcastTransaction(tx, txid, err_string, highfee);
+    if (TransactionError::OK != err) {
         throw JSONRPCTransactionError(err, err_string);
     }
 
@@ -1493,8 +1494,8 @@ UniValue combinepsbt(const JSONRPCRequest& request)
     }
 
     PartiallySignedTransaction merged_psbt;
-    TransactionError error;
-    if (!CombinePSBTs(merged_psbt, error, psbtxs)) {
+    const TransactionError error = CombinePSBTs(merged_psbt, psbtxs);
+    if (error != TransactionError::OK) {
         throw JSONRPCTransactionError(error);
     }
 
diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index 023b4b6746..86695bc1a5 100644
--- a/src/rpc/util.cpp
+++ b/src/rpc/util.cpp
@@ -1,11 +1,10 @@
-// Copyright (c) 2017-2018 The Bitcoin Core developers
+// Copyright (c) 2017-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <key_io.h>
 #include <keystore.h>
 #include <policy/fees.h>
-#include <rpc/protocol.h>
 #include <rpc/util.h>
 #include <tinyformat.h>
 #include <util/strencodings.h>
@@ -315,6 +314,17 @@ std::string RPCExamples::ToDescriptionString() const
     return m_examples.empty() ? m_examples : "\nExamples:\n" + m_examples;
 }
 
+bool RPCHelpMan::IsValidNumArgs(size_t num_args) const
+{
+    size_t num_required_args = 0;
+    for (size_t n = m_args.size(); n > 0; --n) {
+        if (!m_args.at(n - 1).IsOptional()) {
+            num_required_args = n;
+            break;
+        }
+    }
+    return num_required_args <= num_args && num_args <= m_args.size();
+}
 std::string RPCHelpMan::ToString() const
 {
     std::string ret;
@@ -323,12 +333,7 @@ std::string RPCHelpMan::ToString() const
     ret += m_name;
     bool was_optional{false};
     for (const auto& arg : m_args) {
-        bool optional;
-        if (arg.m_fallback.which() == 1) {
-            optional = true;
-        } else {
-            optional = RPCArg::Optional::NO != boost::get<RPCArg::Optional>(arg.m_fallback);
-        }
+        const bool optional = arg.IsOptional();
         ret += " ";
         if (optional) {
             if (!was_optional) ret += "( ";
@@ -370,6 +375,15 @@ std::string RPCHelpMan::ToString() const
     return ret;
 }
 
+bool RPCArg::IsOptional() const
+{
+    if (m_fallback.which() == 1) {
+        return true;
+    } else {
+        return RPCArg::Optional::NO != boost::get<RPCArg::Optional>(m_fallback);
+    }
+}
+
 std::string RPCArg::ToDescriptionString() const
 {
     std::string ret;
diff --git a/src/rpc/util.h b/src/rpc/util.h
index 1c9ddcdf44..06800ad63c 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2017-2018 The Bitcoin Core developers
+// Copyright (c) 2017-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -7,6 +7,7 @@
 
 #include <node/transaction.h>
 #include <pubkey.h>
+#include <rpc/protocol.h>
 #include <script/standard.h>
 #include <univalue.h>
 
@@ -53,7 +54,7 @@ struct RPCArg {
         /** Required arg */
         NO,
         /**
-         * Optinal arg that is a named argument and has a default value of
+         * Optional arg that is a named argument and has a default value of
          * `null`. When possible, the default value should be specified.
          */
         OMITTED_NAMED_ARG,
@@ -110,6 +111,8 @@ struct RPCArg {
         assert(type == Type::ARR || type == Type::OBJ);
     }
 
+    bool IsOptional() const;
+
     /**
      * Return the type string of the argument.
      * Set oneline to allow it to be overridden by a custom oneline type string (m_oneline_description).
@@ -185,6 +188,8 @@ public:
     RPCHelpMan(std::string name, std::string description, std::vector<RPCArg> args, RPCResults results, RPCExamples examples);
 
     std::string ToString() const;
+    /** If the supplied number of args is neither too small nor too high */
+    bool IsValidNumArgs(size_t num_args) const;
 
 private:
     const std::string m_name;
diff --git a/src/wallet/psbtwallet.cpp b/src/wallet/psbtwallet.cpp
index 761e7b7dd7..1b17b09763 100644
--- a/src/wallet/psbtwallet.cpp
+++ b/src/wallet/psbtwallet.cpp
@@ -4,7 +4,7 @@
 
 #include <wallet/psbtwallet.h>
 
-bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, TransactionError& error, bool& complete, int sighash_type, bool sign, bool bip32derivs)
+TransactionError FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, bool& complete, int sighash_type, bool sign, bool bip32derivs)
 {
     LOCK(pwallet->cs_wallet);
     // Get all of the previous transactions
@@ -19,8 +19,7 @@ bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, Transac
 
         // Verify input looks sane. This will check that we have at most one uxto, witness or non-witness.
         if (!input.IsSane()) {
-            error = TransactionError::INVALID_PSBT;
-            return false;
+            return TransactionError::INVALID_PSBT;
         }
 
         // If we have no utxo, grab it from the wallet.
@@ -37,8 +36,7 @@ bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, Transac
 
         // Get the Sighash type
         if (sign && input.sighash_type > 0 && input.sighash_type != sighash_type) {
-            error = TransactionError::SIGHASH_MISMATCH;
-            return false;
+            return TransactionError::SIGHASH_MISMATCH;
         }
 
         complete &= SignPSBTInput(HidingSigningProvider(pwallet, !sign, !bip32derivs), psbtx, i, sighash_type);
@@ -58,5 +56,5 @@ bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, Transac
         psbt_out.FromSignatureData(sigdata);
     }
 
-    return true;
+    return TransactionError::OK;
 }
diff --git a/src/wallet/psbtwallet.h b/src/wallet/psbtwallet.h
index b679f5c6ba..a24a0967d2 100644
--- a/src/wallet/psbtwallet.h
+++ b/src/wallet/psbtwallet.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2009-2018 The Bitcoin Core developers
+// Copyright (c) 2009-2019 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -18,16 +18,14 @@
  *
  * @param[in]  pwallet pointer to a wallet
  * @param[in]  &psbtx reference to PartiallySignedTransaction to fill in
- * @param[out] &error reference to UniValue to fill with error info on failure
  * @param[out] &complete indicates whether the PSBT is now complete
  * @param[in]  sighash_type the sighash type to use when signing (if PSBT does not specify)
  * @param[in]  sign whether to sign or not
  * @param[in]  bip32derivs whether to fill in bip32 derivation information if available
- * return true on success, false on error (and fills in `error`)
+ * return error
  */
-bool FillPSBT(const CWallet* pwallet,
+NODISCARD TransactionError FillPSBT(const CWallet* pwallet,
               PartiallySignedTransaction& psbtx,
-              TransactionError& error,
               bool& complete,
               int sighash_type = 1 /* SIGHASH_ALL */,
               bool sign = true,
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 37fc88dfd5..97c6c38be1 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -4007,8 +4007,8 @@ UniValue walletprocesspsbt(const JSONRPCRequest& request)
     bool sign = request.params[1].isNull() ? true : request.params[1].get_bool();
     bool bip32derivs = request.params[3].isNull() ? false : request.params[3].get_bool();
     bool complete = true;
-    TransactionError err;
-    if (!FillPSBT(pwallet, psbtx, err, complete, nHashType, sign, bip32derivs)) {
+    const TransactionError err = FillPSBT(pwallet, psbtx, complete, nHashType, sign, bip32derivs);
+    if (err != TransactionError::OK) {
         throw JSONRPCTransactionError(err);
     }
 
@@ -4125,8 +4125,8 @@ UniValue walletcreatefundedpsbt(const JSONRPCRequest& request)
     // Fill transaction with out data but don't sign
     bool bip32derivs = request.params[4].isNull() ? false : request.params[4].get_bool();
     bool complete = true;
-    TransactionError err;
-    if (!FillPSBT(pwallet, psbtx, err, complete, 1, false, bip32derivs)) {
+    const TransactionError err = FillPSBT(pwallet, psbtx, complete, 1, false, bip32derivs);
+    if (err != TransactionError::OK) {
         throw JSONRPCTransactionError(err);
     }
 
diff --git a/src/wallet/test/psbt_wallet_tests.cpp b/src/wallet/test/psbt_wallet_tests.cpp
index 2a3149de46..789e86e21b 100644
--- a/src/wallet/test/psbt_wallet_tests.cpp
+++ b/src/wallet/test/psbt_wallet_tests.cpp
@@ -62,9 +62,8 @@ BOOST_AUTO_TEST_CASE(psbt_updater_test)
     ssData >> psbtx;
 
     // Fill transaction with our data
-    TransactionError err;
     bool complete = true;
-    FillPSBT(&m_wallet, psbtx, err, complete, SIGHASH_ALL, false, true);
+    BOOST_REQUIRE_EQUAL(TransactionError::OK, FillPSBT(&m_wallet, psbtx, complete, SIGHASH_ALL, false, true));
 
     // Get the final tx
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
diff --git a/test/functional/rpc_getblockstats.py b/test/functional/rpc_getblockstats.py
index ca9e24367a..feba16f1b3 100755
--- a/test/functional/rpc_getblockstats.py
+++ b/test/functional/rpc_getblockstats.py
@@ -178,5 +178,10 @@ class GetblockstatsTest(BitcoinTestFramework):
         assert_raises_rpc_error(-5, 'Block not found', self.nodes[0].getblockstats,
                                 hash_or_height='000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f')
 
+        # Invalid number of args
+        assert_raises_rpc_error(-1, 'getblockstats hash_or_height ( stats )', self.nodes[0].getblockstats, '00', 1, 2)
+        assert_raises_rpc_error(-1, 'getblockstats hash_or_height ( stats )', self.nodes[0].getblockstats)
+
+
 if __name__ == '__main__':
     GetblockstatsTest().main()