diff --git a/src/main.cpp b/src/main.cpp
index faf643b3c5..e2a1f31228 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3643,7 +3643,7 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, const Co
     return true;
 }
 
-static bool AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex=NULL)
+static bool AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex)
 {
     AssertLockHeld(cs_main);
     // Check for duplicate
@@ -3692,6 +3692,21 @@ static bool AcceptBlockHeader(const CBlockHeader& block, CValidationState& state
     return true;
 }
 
+// Exposed wrapper for AcceptBlockHeader
+bool ProcessNewBlockHeaders(const std::vector<CBlockHeader>& headers, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex)
+{
+    {
+        LOCK(cs_main);
+        for (const CBlockHeader& header : headers) {
+            if (!AcceptBlockHeader(header, state, chainparams, ppindex)) {
+                return false;
+            }
+        }
+    }
+    NotifyHeaderTip();
+    return true;
+}
+
 /** Store block on disk. If dbp is non-NULL, the file is known to already reside on disk */
 static bool AcceptBlock(const CBlock& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex, bool fRequested, const CDiskBlockPos* dbp, bool* fNewBlock)
 {
@@ -5754,6 +5769,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         CBlockHeaderAndShortTxIDs cmpctblock;
         vRecv >> cmpctblock;
 
+        {
         LOCK(cs_main);
 
         if (mapBlockIndex.find(cmpctblock.header.hashPrevBlock) == mapBlockIndex.end()) {
@@ -5762,19 +5778,23 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                 connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
             return true;
         }
+        }
 
         CBlockIndex *pindex = NULL;
         CValidationState state;
-        if (!AcceptBlockHeader(cmpctblock.header, state, chainparams, &pindex)) {
+        if (!ProcessNewBlockHeaders({cmpctblock.header}, state, chainparams, &pindex)) {
             int nDoS;
             if (state.IsInvalid(nDoS)) {
-                if (nDoS > 0)
+                if (nDoS > 0) {
+                    LOCK(cs_main);
                     Misbehaving(pfrom->GetId(), nDoS);
+                }
                 LogPrintf("Peer %d sent us invalid header via cmpctblock\n", pfrom->id);
                 return true;
             }
         }
 
+        LOCK(cs_main);
         // If AcceptBlockHeader returned true, it set pindex
         assert(pindex);
         UpdateBlockAvailability(pfrom->GetId(), pindex->GetBlockHash());
@@ -5968,14 +5988,14 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             ReadCompactSize(vRecv); // ignore tx count; assume it is 0.
         }
 
-        {
-        LOCK(cs_main);
-
         if (nCount == 0) {
             // Nothing interesting. Stop asking this peers for more headers.
             return true;
         }
 
+        CBlockIndex *pindexLast = NULL;
+        {
+        LOCK(cs_main);
         CNodeState *nodestate = State(pfrom->GetId());
 
         // If this looks like it could be a block announcement (nCount <
@@ -6005,23 +6025,31 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             return true;
         }
 
-        CBlockIndex *pindexLast = NULL;
-        BOOST_FOREACH(const CBlockHeader& header, headers) {
-            CValidationState state;
-            if (pindexLast != NULL && header.hashPrevBlock != pindexLast->GetBlockHash()) {
+        uint256 hashLastBlock;
+        for (const CBlockHeader& header : headers) {
+            if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) {
                 Misbehaving(pfrom->GetId(), 20);
                 return error("non-continuous headers sequence");
             }
-            if (!AcceptBlockHeader(header, state, chainparams, &pindexLast)) {
-                int nDoS;
-                if (state.IsInvalid(nDoS)) {
-                    if (nDoS > 0)
-                        Misbehaving(pfrom->GetId(), nDoS);
-                    return error("invalid header received");
+            hashLastBlock = header.GetHash();
+        }
+        }
+
+        CValidationState state;
+        if (!ProcessNewBlockHeaders(headers, state, chainparams, &pindexLast)) {
+            int nDoS;
+            if (state.IsInvalid(nDoS)) {
+                if (nDoS > 0) {
+                    LOCK(cs_main);
+                    Misbehaving(pfrom->GetId(), nDoS);
                 }
+                return error("invalid header received");
             }
         }
 
+        {
+        LOCK(cs_main);
+        CNodeState *nodestate = State(pfrom->GetId());
         if (nodestate->nUnconnectingHeaders > 0) {
             LogPrint("net", "peer=%d: resetting nUnconnectingHeaders (%d -> 0)\n", pfrom->id, nodestate->nUnconnectingHeaders);
         }
@@ -6093,8 +6121,6 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
             }
         }
         }
-
-        NotifyHeaderTip();
     }
 
     else if (strCommand == NetMsgType::BLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
diff --git a/src/main.h b/src/main.h
index c98ed05726..6b2668e568 100644
--- a/src/main.h
+++ b/src/main.h
@@ -223,6 +223,8 @@ static const uint64_t MIN_DISK_SPACE_FOR_BLOCK_FILES = 550 * 1024 * 1024;
  * Note that we guarantee that either the proof-of-work is valid on pblock, or
  * (and possibly also) BlockChecked will have been called.
  * 
+ * Call without cs_main held.
+ *
  * @param[in]   pblock  The block we want to process.
  * @param[in]   fForceProcessing Process this block even if unrequested; used for non-network block sources and whitelisted peers.
  * @param[out]  dbp     The already known disk position of pblock, or NULL if not yet stored.
@@ -230,6 +232,19 @@ static const uint64_t MIN_DISK_SPACE_FOR_BLOCK_FILES = 550 * 1024 * 1024;
  * @return True if state.IsValid()
  */
 bool ProcessNewBlock(const CChainParams& chainparams, const CBlock* pblock, bool fForceProcessing, const CDiskBlockPos* dbp, bool* fNewBlock);
+
+/**
+ * Process incoming block headers.
+ *
+ * Call without cs_main held.
+ *
+ * @param[in]  block The block headers themselves
+ * @param[out] state This may be set to an Error state if any error occurred processing them
+ * @param[in]  chainparams The params for the chain we want to connect to
+ * @param[out] ppindex If set, the pointer will be set to point to the last new block index object for the given headers
+ */
+bool ProcessNewBlockHeaders(const std::vector<CBlockHeader>& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex=NULL);
+
 /** Check whether enough disk space is available for an incoming block */
 bool CheckDiskSpace(uint64_t nAdditionalBytes = 0);
 /** Open a block file (blk?????.dat) */