diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -649,6 +649,43 @@
         !wallet->GetNewDestination(OutputType::LEGACY, "", dest, error));
 }
 
+// Explicit calculation which is used to test the wallet constant
+static size_t CalculateP2PKHInputSize(bool use_max_sig) {
+    // Generate ephemeral valid pubkey
+    CKey key;
+    key.MakeNewKey(true);
+    CPubKey pubkey = key.GetPubKey();
+
+    // Generate pubkey hash
+    PKHash key_hash(pubkey);
+
+    // Create script to enter into keystore. Key hash can't be 0...
+    CScript script = GetScriptForDestination(key_hash);
+
+    // Add script to key store and key to watchonly
+    FillableSigningProvider keystore;
+    keystore.AddKeyPubKey(key, pubkey);
+
+    // Fill in dummy signatures for fee calculation.
+    SignatureData sig_data;
+    if (!ProduceSignature(keystore,
+                          use_max_sig ? DUMMY_MAXIMUM_SIGNATURE_CREATOR
+                                      : DUMMY_SIGNATURE_CREATOR,
+                          script, sig_data)) {
+        // We're hand-feeding it correct arguments; shouldn't happen
+        assert(false);
+    }
+
+    CTxIn tx_in;
+    UpdateInput(tx_in, sig_data);
+    return (size_t)GetVirtualTransactionInputSize(tx_in);
+}
+
+BOOST_FIXTURE_TEST_CASE(dummy_input_size_test, TestChain100Setup) {
+    BOOST_CHECK(CalculateP2PKHInputSize(false) <= DUMMY_P2PKH_INPUT_SIZE);
+    BOOST_CHECK_EQUAL(CalculateP2PKHInputSize(true), DUMMY_P2PKH_INPUT_SIZE);
+}
+
 bool malformed_descriptor(std::ios_base::failure e) {
     std::string s(e.what());
     return s.find("Missing checksum") != std::string::npos;
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -107,6 +107,8 @@
 //! -maxtxfee will warn if called with a higher fee than this amount (in
 //! satoshis)
 constexpr Amount HIGH_MAX_TX_FEE{100 * HIGH_TX_FEE_PER_KB};
+//! Pre-calculated constants for input size estimation
+static constexpr size_t DUMMY_P2PKH_INPUT_SIZE = 148;
 
 class CChainParams;
 class CCoinControl;
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1647,8 +1647,6 @@
     CMutableTransaction txn;
     txn.vin.push_back(CTxIn(COutPoint()));
     if (!wallet->DummySignInput(txn.vin[0], txout, use_max_sig)) {
-        // This should never happen, because IsAllFromMe(ISMINE_SPENDABLE)
-        // implies that we can sign for every input.
         return -1;
     }
     return GetSerializeSize(txn.vin[0], PROTOCOL_VERSION);
@@ -3160,9 +3158,17 @@
             if (pick_new_inputs) {
                 nValueIn = Amount::zero();
                 setCoins.clear();
-                coin_selection_params.change_spend_size =
-                    CalculateMaximumSignedInputSize(change_prototype_txout,
-                                                    this);
+                int change_spend_size = CalculateMaximumSignedInputSize(
+                    change_prototype_txout, this);
+                // If the wallet doesn't know how to sign change output, assume
+                // p2pkh as lower-bound to allow BnB to do it's thing
+                if (change_spend_size == -1) {
+                    coin_selection_params.change_spend_size =
+                        DUMMY_P2PKH_INPUT_SIZE;
+                } else {
+                    coin_selection_params.change_spend_size =
+                        size_t(change_spend_size);
+                }
                 coin_selection_params.effective_fee = nFeeRateNeeded;
                 if (!SelectCoins(vAvailableCoins, nValueToSelect, setCoins,
                                  nValueIn, coin_control, coin_selection_params,
diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
--- a/test/functional/rpc_psbt.py
+++ b/test/functional/rpc_psbt.py
@@ -189,8 +189,18 @@
         self.nodes[0].generate(6)
         self.sync_all()
 
+        block_height = self.nodes[0].getblockcount()
         unspent = self.nodes[0].listunspent()[0]
 
+        # Make sure change address wallet does not have P2SH innerscript access to results in success
+        # when attempting BnB coin selection
+        self.nodes[0].walletcreatefundedpsbt(
+            [],
+            [{self.nodes[2].getnewaddress():unspent["amount"] + 1}],
+            block_height + 2,
+            {"changeAddress": self.nodes[1].getnewaddress()},
+            False)
+
         # Regression test for 14473 (mishandling of already-signed
         # transaction):
         psbtx_info = self.nodes[0].walletcreatefundedpsbt([{"txid": unspent["txid"], "vout":unspent["vout"]}], [