diff --git a/src/main.cpp b/src/main.cpp
index 510fe6f18..12b405a95 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1283,6 +1283,16 @@ bool ContextualCheckTransaction(int32_t slowflag,const CBlock *block, CBlockInde
     const bool overwinterActive = nHeight >=1 ? true : false; //NetworkUpgradeActive(nHeight, Params().GetConsensus(), Consensus::UPGRADE_OVERWINTER);
     const bool saplingActive    = nHeight >=1 ? true : false; //NetworkUpgradeActive(nHeight, Params().GetConsensus(), Consensus::UPGRADE_SAPLING);
 
+    // SECURITY FIX (JoinSplit inflation): reject Sprout JoinSplits at consensus. DragonX is
+    // Sapling-only from genesis (zero JoinSplits in its entire history, verified by the mainnet
+    // supply audit); a tx carrying one is illegitimate. Their zk-proof/sig/nullifier/anchor are
+    // never verified while vpub_new is counted as transparent value-in -> unlimited inflation.
+    // Coinbase/notary (IsMint) exempt. Unconditional is safe: no historical block has a JoinSplit.
+    if (!tx.IsMint() && !tx.vjoinsplit.empty()) {
+        return state.DoS(100, error("ContextualCheckTransaction(): Sprout JoinSplits are disabled (inflation vector)"),
+                         REJECT_INVALID, "bad-txns-joinsplit-disabled");
+    }
+
     if (saplingActive) {
         // Reject transactions with valid version but missing overwintered flag
         if (tx.nVersion >= SAPLING_MIN_TX_VERSION && !tx.fOverwintered) {