diff --git a/src/main.cpp b/src/main.cpp
index 48f5dae4f..c98f42d7c 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -2922,14 +2922,15 @@ static void NotifyHeaderTip() {
  */
 bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, const CBlock *pblock) {
     CBlockIndex *pindexMostWork = NULL;
+    CBlockIndex *pindexNewTip = NULL;
     do {
         boost::this_thread::interruption_point();
         if (ShutdownRequested())
             break;
 
-        CBlockIndex *pindexNewTip = NULL;
         const CBlockIndex *pindexFork;
         bool fInitialDownload;
+        int nNewHeight;
         {
             LOCK(cs_main);
             CBlockIndex *pindexOldTip = chainActive.Tip();
@@ -2952,6 +2953,7 @@ bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams,
             pindexNewTip = chainActive.Tip();
             pindexFork = chainActive.FindFork(pindexOldTip);
             fInitialDownload = IsInitialBlockDownload();
+            nNewHeight = chainActive.Height();
         }
         // When we reach this point, we switched to a new tip (stored in pindexNewTip).
 
@@ -2980,7 +2982,7 @@ bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams,
                 {
                     LOCK(cs_vNodes);
                     BOOST_FOREACH(CNode* pnode, vNodes) {
-                        if (chainActive.Height() > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : nBlockEstimate)) {
+                        if (nNewHeight > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : nBlockEstimate)) {
                             BOOST_REVERSE_FOREACH(const uint256& hash, vHashes) {
                                 pnode->PushBlockHash(hash);
                             }
@@ -2993,7 +2995,7 @@ bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams,
                 }
             }
         }
-    } while(pindexMostWork != chainActive.Tip());
+    } while (pindexNewTip != pindexMostWork);
     CheckBlockIndex(chainparams.GetConsensus());
 
     // Write changes periodically to disk, after relay.
@@ -4569,6 +4571,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                strCommand == NetMsgType::FILTERCLEAR))
     {
         if (pfrom->nVersion >= NO_BLOOM_VERSION) {
+            LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 100);
             return false;
         } else {
@@ -4584,6 +4587,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         if (pfrom->nVersion != 0)
         {
             pfrom->PushMessage(NetMsgType::REJECT, strCommand, REJECT_DUPLICATE, string("Duplicate version message"));
+            LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 1);
             return false;
         }
@@ -4643,7 +4647,10 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         pfrom->fClient = !(pfrom->nServices & NODE_NETWORK);
 
         // Potentially mark this peer as a preferred download peer.
+        {
+        LOCK(cs_main);
         UpdatePreferredDownload(pfrom, State(pfrom->GetId()));
+        }
 
         // Change version
         pfrom->PushMessage(NetMsgType::VERACK);
@@ -4701,6 +4708,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
     else if (pfrom->nVersion == 0)
     {
         // Must have a version message before anything else
+        LOCK(cs_main);
         Misbehaving(pfrom->GetId(), 1);
         return false;
     }
@@ -4736,6 +4744,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             return true;
         if (vAddr.size() > 1000)
         {
+            LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 20);
             return error("message addr size() = %u", vAddr.size());
         }
@@ -4803,6 +4812,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         vRecv >> vInv;
         if (vInv.size() > MAX_INV_SZ)
         {
+            LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 20);
             return error("message inv size() = %u", vInv.size());
         }
@@ -4878,6 +4888,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         vRecv >> vInv;
         if (vInv.size() > MAX_INV_SZ)
         {
+            LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 20);
             return error("message getdata size() = %u", vInv.size());
         }
@@ -5129,6 +5140,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         // Bypass the normal CBlock deserialization, as we don't want to risk deserializing 2000 full blocks.
         unsigned int nCount = ReadCompactSize(vRecv);
         if (nCount > MAX_HEADERS_RESULTS) {
+            LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 20);
             return error("headers message size = %u", nCount);
         }
@@ -5390,8 +5402,11 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         LOCK(pfrom->cs_filter);
 
         if (!filter.IsWithinSizeConstraints())
+        {
             // There is no excuse for sending a too-large filter
+            LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 100);
+        }
         else
         {
             delete pfrom->pfilter;
@@ -5411,13 +5426,17 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         // and thus, the maximum size any matched object can have) in a filteradd message
         if (vData.size() > MAX_SCRIPT_ELEMENT_SIZE)
         {
+            LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 100);
         } else {
             LOCK(pfrom->cs_filter);
             if (pfrom->pfilter)
                 pfrom->pfilter->insert(vData);
             else
+            {
+                LOCK(cs_main);
                 Misbehaving(pfrom->GetId(), 100);
+            }
         }
     }