diff --git a/src/libxrpl/tx/transactors/lending/LoanManage.cpp b/src/libxrpl/tx/transactors/lending/LoanManage.cpp
index a312dba3b3..7bccbd71ec 100644
--- a/src/libxrpl/tx/transactors/lending/LoanManage.cpp
+++ b/src/libxrpl/tx/transactors/lending/LoanManage.cpp
@@ -165,8 +165,6 @@ LoanManage::defaultLoan(
         return std::min(covered, coverAvailable);
     }();
 
-    auto const vaultDefaultAmount = totalDefaultAmount - defaultCovered;
-
     // Update the Vault object:
 
     // The vault may be at a different scale than the loan. Reduce rounding
@@ -174,7 +172,64 @@ LoanManage::defaultLoan(
     // scale.
     auto const vaultScale = getAssetsTotalScale(vaultSle);
 
+    // Under fixCleanup3_4_0, both vault-side fields are mutated through a
+    // single asset-typed STAmount pair. `amount = STAmount{vaultAsset,
+    // defaultCovered}` is applied to both sfAssetsTotal and
+    // sfAssetsAvailable, and `writeOff = STAmount{vaultAsset,
+    // totalDefaultAmount}` is applied to sfAssetsTotal only. Because the
+    // shared `amount` is normalized to STAmount precision exactly once and
+    // absorbed by both fields symmetrically, sfAssetsAvailable cannot
+    // overshoot sfAssetsTotal from arithmetic alone -- the residual is
+    // exactly `-writeOff` on Total. Pre-amendment, the two fields were
+    // adjusted via values obtained through different Number->STAmount
+    // paths (vaultDefaultAmount rounded down to vaultScale on one side,
+    // defaultCovered kept at the finer loan scale on the other), so the
+    // normalization was asymmetric and a dust-reconciliation snap was
+    // required to paper over the resulting cross-side mismatch -- a snap
+    // that itself minted phantom assets on sfAssetsTotal. See the
+    // sibling change in LoanPay for the same fix on the payment path.
+    bool const useUnifiedAssetArithmetic = view.rules().enabled(fixCleanup3_4_0);
+
+    if (useUnifiedAssetArithmetic)
     {
+        // Prior to realizing the default, the vault must already carry
+        // at least this loan's exposure. A violation here is a corrupt
+        // ledger, not a transaction-input error.
+        //
+        // This guard is strictly stronger than the pre-amendment
+        // `vaultTotalBefore < vaultDefaultAmount` form, but activation is
+        // safe: the ValidVault invariant continuously enforces Total >=
+        // Available (so Total - Available >= 0 on every ledger), and the
+        // pre-amendment cross-scale rounding could only inflate the
+        // difference Total - Available, never deflate it. Any ledger
+        // reaching this point post-activation will therefore already
+        // satisfy the stronger form.
+        Number const vaultTotalBefore = *vaultSle->at(sfAssetsTotal);
+        Number const vaultAvailableBefore = *vaultSle->at(sfAssetsAvailable);
+        if (vaultTotalBefore - vaultAvailableBefore < totalDefaultAmount)
+        {
+            // LCOV_EXCL_START
+            JLOG(j.warn()) << "Vault exposure is less than the loan default amount";
+            return tefBAD_LEDGER;
+            // LCOV_EXCL_STOP
+        }
+
+        // Mutate the two vault fields through a single asset-typed pair
+        // (see the block comment on useUnifiedAssetArithmetic above for
+        // why this is safe):
+        //   (1) write off totalDefaultAmount from Total only;
+        //   (2) add defaultCovered symmetrically to both fields.
+        STAmount const amount{vaultAsset, defaultCovered};
+        STAmount const writeOff{vaultAsset, totalDefaultAmount};
+
+        vaultSle->at(sfAssetsTotal) += amount - writeOff;
+        vaultSle->at(sfAssetsAvailable) += amount;
+    }
+    else
+    {
+        // Pre-amendment behavior.
+        auto const vaultDefaultAmount = totalDefaultAmount - defaultCovered;
+
         // Decrease the Total Value of the Vault:
         auto vaultTotalProxy = vaultSle->at(sfAssetsTotal);
         auto vaultAvailableProxy = vaultSle->at(sfAssetsAvailable);
@@ -190,8 +245,8 @@ LoanManage::defaultLoan(
         auto const vaultDefaultRounded = roundToAsset(
             vaultAsset, vaultDefaultAmount, vaultScale, Number::RoundingMode::Downward);
         vaultTotalProxy -= vaultDefaultRounded;
-        // Increase the Asset Available of the Vault by liquidated First-Loss
-        // Capital and any unclaimed funds amount:
+        // Increase the Asset Available of the Vault by liquidated
+        // First-Loss Capital and any unclaimed funds amount:
         vaultAvailableProxy += defaultCovered;
         if (*vaultAvailableProxy > *vaultTotalProxy && !vaultAsset.integral())
         {
@@ -203,8 +258,8 @@ LoanManage::defaultLoan(
                             << "(" << difference.exponent() << ")";
             if (vaultAvailableProxy.value().exponent() - difference.exponent() > 13)
             {
-                // If the difference is dust, bring the total up to match
-                // the available
+                // If the difference is dust, bring the total up to
+                // match the available
                 JLOG(j.debug()) << "Difference between vault assets available and total is "
                                    "dust. Set both to the larger value.";
                 vaultTotalProxy = vaultAvailableProxy;
@@ -219,24 +274,24 @@ LoanManage::defaultLoan(
             return tecINTERNAL;
             // LCOV_EXCL_STOP
         }
-
-        // The loss has been realized
-        if (loanSle->isFlag(lsfLoanImpaired))
-        {
-            auto vaultLossUnrealizedProxy = vaultSle->at(sfLossUnrealized);
-            if (vaultLossUnrealizedProxy < totalDefaultAmount)
-            {
-                // LCOV_EXCL_START
-                JLOG(j.warn()) << "Vault unrealized loss is less than the default amount";
-                return tefBAD_LEDGER;
-                // LCOV_EXCL_STOP
-            }
-            adjustImpreciseNumber(
-                vaultLossUnrealizedProxy, -totalDefaultAmount, vaultAsset, vaultScale);
-        }
-        view.update(vaultSle);
     }
 
+    // The loss has been realized
+    if (loanSle->isFlag(lsfLoanImpaired))
+    {
+        auto vaultLossUnrealizedProxy = vaultSle->at(sfLossUnrealized);
+        if (vaultLossUnrealizedProxy < totalDefaultAmount)
+        {
+            // LCOV_EXCL_START
+            JLOG(j.warn()) << "Vault unrealized loss is less than the default amount";
+            return tefBAD_LEDGER;
+            // LCOV_EXCL_STOP
+        }
+        adjustImpreciseNumber(
+            vaultLossUnrealizedProxy, -totalDefaultAmount, vaultAsset, vaultScale);
+    }
+    view.update(vaultSle);
+
     // Update the LoanBroker object:
 
     {
diff --git a/src/test/app/lending/LoanRounding_test.cpp b/src/test/app/lending/LoanRounding_test.cpp
index 5e69c9f79e..3a26134489 100644
--- a/src/test/app/lending/LoanRounding_test.cpp
+++ b/src/test/app/lending/LoanRounding_test.cpp
@@ -987,7 +987,7 @@ public:
     {
         runAmendmentIndependent();
         for (auto const& features : jtx::amendmentCombinations(
-                 {fixCleanup3_1_3, fixCleanup3_2_0, featureMPTokensV2}, all_))
+                 {fixCleanup3_1_3, fixCleanup3_2_0, fixCleanup3_4_0, featureMPTokensV2}, all_))
             runAmendmentSensitive(features);
     }
 };