diff --git a/src/wallet/spend.cpp b/src/wallet/spend.cpp
index 6fbbfbace4..d4c87f1176 100644
--- a/src/wallet/spend.cpp
+++ b/src/wallet/spend.cpp
@@ -140,6 +140,11 @@ TxSize CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *walle
     // Segwit marker and flag
     if (is_segwit) weight += 2;
 
+    // Blackcoin: transaction weight should be increased for v1 transactions because of additional nTime field
+    // We assume that v1 transactions have nTime != 0
+    bool is_old_tx = tx.nTime > 0;
+    if (is_old_tx) weight += 4 * WITNESS_SCALE_FACTOR;
+
     // Add the size of the transaction outputs.
     for (const auto& txo : tx.vout) weight += GetSerializeSize(txo, PROTOCOL_VERSION) * WITNESS_SCALE_FACTOR;