diff --git a/src/main.cpp b/src/main.cpp
index c4d619485..456754353 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -474,6 +474,7 @@ unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
 
 bool IsStandardTx(const CTransaction& tx, string& reason)
 {
+    AssertLockHeld(cs_main);
     if (tx.nVersion > CTransaction::CURRENT_VERSION || tx.nVersion < 1) {
         reason = "version";
         return false;
@@ -556,6 +557,7 @@ bool IsStandardTx(const CTransaction& tx, string& reason)
 
 bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)
 {
+    AssertLockHeld(cs_main);
     // Time based nLockTime implemented in 0.1.6
     if (tx.nLockTime == 0)
         return true;
@@ -667,6 +669,7 @@ unsigned int GetP2SHSigOpCount(const CTransaction& tx, CCoinsViewCache& inputs)
 
 int CMerkleTx::SetMerkleBranch(const CBlock* pblock)
 {
+    AssertLockHeld(cs_main);
     CBlock blockTmp;
 
     if (pblock == NULL) {
@@ -813,6 +816,7 @@ int64_t GetMinFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree,
 bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
                         bool* pfMissingInputs, bool fRejectInsaneFee)
 {
+    AssertLockHeld(cs_main);
     if (pfMissingInputs)
         *pfMissingInputs = false;
 
@@ -958,6 +962,7 @@ int CMerkleTx::GetDepthInMainChainINTERNAL(CBlockIndex* &pindexRet) const
 {
     if (hashBlock == 0 || nIndex == -1)
         return 0;
+    AssertLockHeld(cs_main);
 
     // Find the block it claims to be in
     map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.find(hashBlock);
@@ -981,6 +986,7 @@ int CMerkleTx::GetDepthInMainChainINTERNAL(CBlockIndex* &pindexRet) const
 
 int CMerkleTx::GetDepthInMainChain(CBlockIndex* &pindexRet) const
 {
+    AssertLockHeld(cs_main);
     int nResult = GetDepthInMainChainINTERNAL(pindexRet);
     if (nResult == 0 && !mempool.exists(GetHash()))
         return -1; // Not in chain, not in mempool
@@ -1304,6 +1310,7 @@ int GetNumBlocksOfPeers()
 
 bool IsInitialBlockDownload()
 {
+    AssertLockHeld(cs_main);
     if (fImporting || fReindex || chainActive.Height() < Checkpoints::GetTotalBlocksEstimate())
         return true;
     static int64_t nLastUpdate;
@@ -1323,6 +1330,7 @@ CBlockIndex *pindexBestForkTip = NULL, *pindexBestForkBase = NULL;
 
 void CheckForkWarningConditions()
 {
+    AssertLockHeld(cs_main);
     // Before we get past initial download, we cannot reliably alert about forks
     // (we assume we don't get stuck on a fork before the last checkpoint)
     if (IsInitialBlockDownload())
@@ -1368,6 +1376,7 @@ void CheckForkWarningConditions()
 
 void CheckForkWarningConditionsOnNewFork(CBlockIndex* pindexNewForkTip)
 {
+    AssertLockHeld(cs_main);
     // If we are on a fork that is sufficiently large, set a warning flag
     CBlockIndex* pfork = pindexNewForkTip;
     CBlockIndex* plonger = chainActive.Tip();
@@ -2078,6 +2087,7 @@ void static FindMostWorkChain() {
 
 // Try to activate to the most-work chain (thereby connecting it).
 bool ActivateBestChain(CValidationState &state) {
+    AssertLockHeld(cs_main);
     CBlockIndex *pindexOldTip = chainActive.Tip();
     bool fComplete = false;
     while (!fComplete) {
@@ -2126,6 +2136,7 @@ bool ActivateBestChain(CValidationState &state) {
 
 bool AddToBlockIndex(CBlock& block, CValidationState& state, const CDiskBlockPos& pos)
 {
+    AssertLockHeld(cs_main);
     // Check for duplicate
     uint256 hash = block.GetHash();
     if (mapBlockIndex.count(hash))
@@ -2344,6 +2355,7 @@ bool CheckBlock(const CBlock& block, CValidationState& state, bool fCheckPOW, bo
 
 bool AcceptBlock(CBlock& block, CValidationState& state, CDiskBlockPos* dbp)
 {
+    AssertLockHeld(cs_main);
     // Check for duplicate
     uint256 hash = block.GetHash();
     if (mapBlockIndex.count(hash))
@@ -2455,6 +2467,7 @@ bool CBlockIndex::IsSuperMajority(int minVersion, const CBlockIndex* pstart, uns
 
 int64_t CBlockIndex::GetMedianTime() const
 {
+    AssertLockHeld(cs_main);
     const CBlockIndex* pindex = this;
     for (int i = 0; i < nMedianTimeSpan/2; i++)
     {
@@ -2467,6 +2480,7 @@ int64_t CBlockIndex::GetMedianTime() const
 
 void PushGetBlocks(CNode* pnode, CBlockIndex* pindexBegin, uint256 hashEnd)
 {
+    AssertLockHeld(cs_main);
     // Filter out duplicate requests
     if (pindexBegin == pnode->pindexLastGetBlocksBegin && hashEnd == pnode->hashLastGetBlocksEnd)
         return;
@@ -2983,6 +2997,7 @@ bool InitBlockIndex() {
 
 void PrintBlockTree()
 {
+    AssertLockHeld(cs_main);
     // pre-compute tree structure
     map<CBlockIndex*, vector<CBlockIndex*> > mapNext;
     for (map<uint256, CBlockIndex*>::iterator mi = mapBlockIndex.begin(); mi != mapBlockIndex.end(); ++mi)
diff --git a/src/qt/transactiondesc.cpp b/src/qt/transactiondesc.cpp
index 4aebaa1e7..6391f9bc1 100644
--- a/src/qt/transactiondesc.cpp
+++ b/src/qt/transactiondesc.cpp
@@ -20,6 +20,7 @@
 
 QString TransactionDesc::FormatTxStatus(const CWalletTx& wtx)
 {
+    AssertLockHeld(cs_main);
     if (!IsFinalTx(wtx, chainActive.Height() + 1))
     {
         if (wtx.nLockTime < LOCKTIME_THRESHOLD)
diff --git a/src/qt/transactionrecord.cpp b/src/qt/transactionrecord.cpp
index 703a2b4e7..5a3728f49 100644
--- a/src/qt/transactionrecord.cpp
+++ b/src/qt/transactionrecord.cpp
@@ -150,6 +150,7 @@ QList<TransactionRecord> TransactionRecord::decomposeTransaction(const CWallet *
 
 void TransactionRecord::updateStatus(const CWalletTx &wtx)
 {
+    AssertLockHeld(cs_main);
     // Determine transaction status
 
     // Find the block the tx is in
@@ -234,6 +235,7 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
 
 bool TransactionRecord::statusUpdateNeeded()
 {
+    AssertLockHeld(cs_main);
     return status.cur_num_blocks != chainActive.Height();
 }