diff --git a/src/main.cpp b/src/main.cpp
index c23aae32..a4f90dda 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -111,10 +111,10 @@ void static EraseFromWallets(uint256 hash)
 }
 
 // make sure all wallets know about the given transaction, in the given block
-void SyncWithWallets(const CTransaction& tx, const CBlock* pblock, bool fUpdate)
+void SyncWithWallets(const uint256 &hash, const CTransaction& tx, const CBlock* pblock, bool fUpdate)
 {
     BOOST_FOREACH(CWallet* pwallet, setpwalletRegistered)
-        pwallet->AddToWalletIfInvolvingMe(tx, pblock, fUpdate);
+        pwallet->AddToWalletIfInvolvingMe(hash, tx, pblock, fUpdate);
 }
 
 // notify wallets about a new best chain
@@ -1197,10 +1197,8 @@ unsigned int CTransaction::GetP2SHSigOpCount(CCoinsView& inputs) const
     return nSigOps;
 }
 
-bool CTransaction::UpdateCoins(CCoinsView &inputs, CTxUndo &txundo, int nHeight) const
+bool CTransaction::UpdateCoins(CCoinsView &inputs, CTxUndo &txundo, int nHeight, const uint256 &txhash) const
 {
-    uint256 hash = GetHash();
-
     // mark inputs spent
     if (!IsCoinBase()) {
         BOOST_FOREACH(const CTxIn &txin, vin) {
@@ -1217,7 +1215,7 @@ bool CTransaction::UpdateCoins(CCoinsView &inputs, CTxUndo &txundo, int nHeight)
     }
 
     // add outputs
-    if (!inputs.SetCoins(hash, CCoins(*this, nHeight)))
+    if (!inputs.SetCoins(txhash, CCoins(*this, nHeight)))
         return error("UpdateCoins() : cannot update output");
 
     return true;
@@ -1467,8 +1465,8 @@ bool CBlock::ConnectBlock(CBlockIndex* pindex, CCoinsView &view, bool fJustCheck
     bool fEnforceBIP30 = !((pindex->nHeight==91842 && pindex->GetBlockHash() == uint256("0x00000000000a4d0a398161ffc163c503763b1f4360639393e0e4c8e300e0caec")) ||
                            (pindex->nHeight==91880 && pindex->GetBlockHash() == uint256("0x00000000000743f190a18c5577a3c2d2a1f610ae9601ac046a38084ccb7cd721")));
     if (fEnforceBIP30) {
-        BOOST_FOREACH(CTransaction& tx, vtx) {
-            uint256 hash = tx.GetHash();
+        for (unsigned int i=0; i<vtx.size(); i++) {
+            uint256 hash = GetTxHash(i);
             CCoins coins;
             if (view.GetCoins(hash, coins) && !coins.IsPruned())
                 return error("ConnectBlock() : tried to overwrite transaction");
@@ -1483,8 +1481,10 @@ bool CBlock::ConnectBlock(CBlockIndex* pindex, CCoinsView &view, bool fJustCheck
 
     int64 nFees = 0;
     unsigned int nSigOps = 0;
-    BOOST_FOREACH(CTransaction& tx, vtx)
+    for (unsigned int i=0; i<vtx.size(); i++)
     {
+        const CTransaction &tx = vtx[i];
+
         nSigOps += tx.GetLegacySigOpCount();
         if (nSigOps > MAX_BLOCK_SIGOPS)
             return DoS(100, error("ConnectBlock() : too many sigops"));
@@ -1511,7 +1511,7 @@ bool CBlock::ConnectBlock(CBlockIndex* pindex, CCoinsView &view, bool fJustCheck
         }
 
         CTxUndo txundo;
-        if (!tx.UpdateCoins(view, txundo, pindex->nHeight))
+        if (!tx.UpdateCoins(view, txundo, pindex->nHeight, GetTxHash(i)))
             return error("ConnectBlock() : UpdateInputs failed");
         if (!tx.IsCoinBase())
             blockundo.vtxundo.push_back(txundo);
@@ -1542,8 +1542,8 @@ bool CBlock::ConnectBlock(CBlockIndex* pindex, CCoinsView &view, bool fJustCheck
         return false;
 
     // Watch for transactions paying to me
-    BOOST_FOREACH(CTransaction& tx, vtx)
-        SyncWithWallets(tx, this, true);
+    for (unsigned int i=0; i<vtx.size(); i++)
+        SyncWithWallets(GetTxHash(i), vtx[i], this, true);
 
     return true;
 }
@@ -1755,7 +1755,7 @@ bool CBlock::AddToBlockIndex(const CDiskBlockPos &pos)
         // Notify UI to display prev block's coinbase if it was ours
         static uint256 hashPrevBestCoinBase;
         UpdatedTransaction(hashPrevBestCoinBase);
-        hashPrevBestCoinBase = vtx[0].GetHash();
+        hashPrevBestCoinBase = GetTxHash(0);
     }
 
     uiInterface.NotifyBlocksChanged();
@@ -1876,10 +1876,10 @@ bool CBlock::CheckBlock(bool fCheckPOW, bool fCheckMerkleRoot) const
 
     // Check for duplicate txids. This is caught by ConnectInputs(),
     // but catching it earlier avoids a potential DoS attack:
+    BuildMerkleTree();
     set<uint256> uniqueTx;
-    BOOST_FOREACH(const CTransaction& tx, vtx)
-    {
-        uniqueTx.insert(tx.GetHash());
+    for (unsigned int i=0; i<vtx.size(); i++) {
+        uniqueTx.insert(GetTxHash(i));
     }
     if (uniqueTx.size() != vtx.size())
         return DoS(100, error("CheckBlock() : duplicate transaction"));
@@ -2914,7 +2914,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
         bool fMissingInputs = false;
         if (tx.AcceptToMemoryPool(true, &fMissingInputs))
         {
-            SyncWithWallets(tx, NULL, true);
+            SyncWithWallets(inv.hash, tx, NULL, true);
             RelayMessage(inv, vMsg);
             mapAlreadyAskedFor.erase(inv);
             vWorkQueue.push_back(inv.hash);
@@ -2937,7 +2937,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
                     if (tx.AcceptToMemoryPool(true, &fMissingInputs2))
                     {
                         printf("   accepted orphan tx %s\n", inv.hash.ToString().substr(0,10).c_str());
-                        SyncWithWallets(tx, NULL, true);
+                        SyncWithWallets(inv.hash, tx, NULL, true);
                         RelayMessage(inv, vMsg);
                         mapAlreadyAskedFor.erase(inv);
                         vWorkQueue.push_back(inv.hash);
@@ -3729,7 +3729,8 @@ CBlock* CreateNewBlock(CReserveKey& reservekey)
                 continue;
 
             CTxUndo txundo;
-            if (!tx.UpdateCoins(viewTemp, txundo, pindexPrev->nHeight+1))
+            uint256 hash = tx.GetHash();
+            if (!tx.UpdateCoins(viewTemp, txundo, pindexPrev->nHeight+1, hash))
                 continue;
 
             // push changes from the second layer cache to the first one
@@ -3749,7 +3750,6 @@ CBlock* CreateNewBlock(CReserveKey& reservekey)
             }
 
             // Add transactions that depend on this one to the priority queue
-            uint256 hash = tx.GetHash();
             if (mapDependers.count(hash))
             {
                 BOOST_FOREACH(COrphan* porphan, mapDependers[hash])
diff --git a/src/main.h b/src/main.h
index 0ec68b61..3ee0108f 100644
--- a/src/main.h
+++ b/src/main.h
@@ -91,7 +91,7 @@ class CCoinsView;
 
 void RegisterWallet(CWallet* pwalletIn);
 void UnregisterWallet(CWallet* pwalletIn);
-void SyncWithWallets(const CTransaction& tx, const CBlock* pblock = NULL, bool fUpdate = false);
+void SyncWithWallets(const uint256 &hash, const CTransaction& tx, const CBlock* pblock = NULL, bool fUpdate = false);
 bool ProcessBlock(CNode* pfrom, CBlock* pblock);
 bool CheckDiskSpace(uint64 nAdditionalBytes=0);
 FILE* OpenBlockFile(const CDiskBlockPos &pos, bool fReadOnly = false);
@@ -577,7 +577,7 @@ public:
     bool CheckInputs(CCoinsView &view, enum CheckSig_mode csmode, bool fStrictPayToScriptHash=true, bool fStrictEncodings=true) const;
 
     // Apply the effects of this transaction on the UTXO set represented by view
-    bool UpdateCoins(CCoinsView &view, CTxUndo &txundo, int nHeight) const;
+    bool UpdateCoins(CCoinsView &view, CTxUndo &txundo, int nHeight, const uint256 &txhash) const;
 
     // Context-independent validity checks
     bool CheckTransaction() const;
@@ -1111,6 +1111,12 @@ public:
         return (vMerkleTree.empty() ? 0 : vMerkleTree.back());
     }
 
+    const uint256 &GetTxHash(unsigned int nIndex) const {
+        assert(vMerkleTree.size() > 0); // BuildMerkleTree must have been called first
+        assert(nIndex < vtx.size());
+        return vMerkleTree[nIndex];
+    }
+
     std::vector<uint256> GetMerkleBranch(int nIndex) const
     {
         if (vMerkleTree.empty())
diff --git a/src/rpcrawtransaction.cpp b/src/rpcrawtransaction.cpp
index 647384f3..72a89c08 100644
--- a/src/rpcrawtransaction.cpp
+++ b/src/rpcrawtransaction.cpp
@@ -517,7 +517,7 @@ Value sendrawtransaction(const Array& params, bool fHelp)
         // Not in block, but already in the memory pool; will drop
         // through to re-relay it.
     } else {
-        SyncWithWallets(tx, NULL, true);
+        SyncWithWallets(hashTx, tx, NULL, true);
     }
     RelayMessage(CInv(MSG_TX, hashTx), tx);
 
diff --git a/src/wallet.cpp b/src/wallet.cpp
index 5b320346..1498ff28 100644
--- a/src/wallet.cpp
+++ b/src/wallet.cpp
@@ -479,9 +479,8 @@ bool CWallet::AddToWallet(const CWalletTx& wtxIn)
 // Add a transaction to the wallet, or update it.
 // pblock is optional, but should be provided if the transaction is known to be in a block.
 // If fUpdate is true, existing transactions will be updated.
-bool CWallet::AddToWalletIfInvolvingMe(const CTransaction& tx, const CBlock* pblock, bool fUpdate, bool fFindBlock)
+bool CWallet::AddToWalletIfInvolvingMe(const uint256 &hash, const CTransaction& tx, const CBlock* pblock, bool fUpdate, bool fFindBlock)
 {
-    uint256 hash = tx.GetHash();
     {
         LOCK(cs_wallet);
         bool fExisted = mapWallet.count(hash);
@@ -756,7 +755,7 @@ int CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, bool fUpdate)
             block.ReadFromDisk(pindex, true);
             BOOST_FOREACH(CTransaction& tx, block.vtx)
             {
-                if (AddToWalletIfInvolvingMe(tx, &block, fUpdate))
+                if (AddToWalletIfInvolvingMe(tx.GetHash(), tx, &block, fUpdate))
                     ret++;
             }
             pindex = pindex->pnext;
diff --git a/src/wallet.h b/src/wallet.h
index 8c98f34a..43b695c5 100644
--- a/src/wallet.h
+++ b/src/wallet.h
@@ -162,7 +162,7 @@ public:
 
     void MarkDirty();
     bool AddToWallet(const CWalletTx& wtxIn);
-    bool AddToWalletIfInvolvingMe(const CTransaction& tx, const CBlock* pblock, bool fUpdate = false, bool fFindBlock = false);
+    bool AddToWalletIfInvolvingMe(const uint256 &hash, const CTransaction& tx, const CBlock* pblock, bool fUpdate = false, bool fFindBlock = false);
     bool EraseFromWallet(uint256 hash);
     void WalletUpdateSpent(const CTransaction& prevout);
     int ScanForWalletTransactions(CBlockIndex* pindexStart, bool fUpdate = false);