diff --git a/src/main.cpp b/src/main.cpp
index 367051629..74615fed7 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4999,6 +4999,7 @@ 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 {
@@ -5020,6 +5021,7 @@ 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;
         }
@@ -5094,7 +5096,10 @@ 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);
@@ -5154,6 +5159,7 @@ 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;
     }
@@ -5199,6 +5205,7 @@ 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());
         }
@@ -5278,6 +5285,7 @@ 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());
         }
@@ -5356,6 +5364,7 @@ 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());
         }
@@ -5846,6 +5855,7 @@ 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);
         }
@@ -6147,8 +6157,11 @@ 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;
@@ -6168,13 +6181,17 @@ 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);
+            }
         }
     }