--- a/src/main.cpp
+++ b/src/main.cpp
@@ -600,7 +600,7 @@
             printf("CTxMemPool::accept() : replacing tx %s with new version\n", ptxOld->GetHash().ToString().c_str());
             remove(*ptxOld);
         }
-        addUnchecked(tx);
+        addUnchecked(hash, tx);
     }
 
     ///// are we sure this is ok when loading transactions or restoring block txes
@@ -619,13 +619,11 @@
     return mempool.accept(txdb, *this, fCheckInputs, pfMissingInputs);
 }
 
-bool CTxMemPool::addUnchecked(CTransaction &tx)
+bool CTxMemPool::addUnchecked(const uint256& hash, CTransaction &tx)
 {
     // Add to memory pool without checking anything.  Don't call this directly,
     // call CTxMemPool::accept to properly check the transaction first.
     {
-        LOCK(cs);
-        uint256 hash = tx.GetHash();
         mapTx[hash] = tx;
         for (unsigned int i = 0; i < tx.vin.size(); i++)
             mapNextTx[tx.vin[i].prevout] = CInPoint(&mapTx[hash], i);
@@ -1325,19 +1323,8 @@
     // This logic is not necessary for memory pool transactions, as AcceptToMemoryPool
     // already refuses previously-known transaction id's entirely.
     // This rule applies to all blocks whose timestamp is after March 15, 2012, 0:00 UTC.
-    if (pindex->nTime > 1331769600)
-    {
-        BOOST_FOREACH(CTransaction& tx, vtx)
-        {
-            CTxIndex txindexOld;
-            if (txdb.ReadTxIndex(tx.GetHash(), txindexOld))
-            {
-                BOOST_FOREACH(CDiskTxPos &pos, txindexOld.vSpent)
-                    if (pos.IsNull())
-                        return false;
-            }
-        }
-    }
+    int64 nBIP30SwitchTime = 1331769600;
+    bool fEnforceBIP30 = (pindex->nTime > nBIP30SwitchTime);
 
     // BIP16 didn't become active until Apr 1 2012
     int64 nBIP16SwitchTime = 1333238400;
@@ -1351,6 +1338,17 @@
     unsigned int nSigOps = 0;
     BOOST_FOREACH(CTransaction& tx, vtx)
     {
+        uint256 hashTx = tx.GetHash();
+
+        if (fEnforceBIP30) {
+            CTxIndex txindexOld;
+            if (txdb.ReadTxIndex(hashTx, txindexOld)) {
+                BOOST_FOREACH(CDiskTxPos &pos, txindexOld.vSpent)
+                    if (pos.IsNull())
+                        return false;
+            }
+        }
+
         nSigOps += tx.GetLegacySigOpCount();
         if (nSigOps > MAX_BLOCK_SIGOPS)
             return DoS(100, error("ConnectBlock() : too many sigops"));
@@ -1381,7 +1379,7 @@
                 return false;
         }
 
-        mapQueuedChanges[tx.GetHash()] = CTxIndex(posThisTx, tx.vout.size());
+        mapQueuedChanges[hashTx] = CTxIndex(posThisTx, tx.vout.size());
     }
 
     // Write queued txindex changes

--- a/src/main.h
+++ b/src/main.h
@@ -1602,7 +1602,7 @@
 
     bool accept(CTxDB& txdb, CTransaction &tx,
                 bool fCheckInputs, bool* pfMissingInputs);
-    bool addUnchecked(CTransaction &tx);
+    bool addUnchecked(const uint256& hash, CTransaction &tx);
     bool remove(CTransaction &tx);
     void queryHashes(std::vector<uint256>& vtxid);