diff --git a/src/net_processing.cpp b/src/net_processing.cpp
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -885,6 +885,9 @@
     /** Return true if the headers connect to each other, false otherwise */
     bool
     CheckHeadersAreContinuous(const std::vector<CBlockHeader> &headers) const;
+    /** Request further headers from this peer from a given block header */
+    void FetchMoreHeaders(CNode &pfrom, const CBlockIndex *pindexLast,
+                          const Peer &peer) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
 
     void SendBlockTransactions(CNode &pfrom, Peer &peer, const CBlock &block,
                                const BlockTransactionsRequest &req);
@@ -3245,6 +3248,31 @@
     return true;
 }
 
+/**
+ * Continue fetching headers from a given point.
+ * pindexLast should be the last header we learned from a peer in their prior
+ * headers message.
+ *
+ * This is used for headers sync with a peer; even if pindexLast is an ancestor
+ * of a known chain (such as our tip) we don't yet know where the peer's chain
+ * might fork from what we know, so we continue exactly from where the peer
+ * left off.
+ */
+void PeerManagerImpl::FetchMoreHeaders(CNode &pfrom,
+                                       const CBlockIndex *pindexLast,
+                                       const Peer &peer) {
+    AssertLockHeld(::cs_main);
+    const CNetMsgMaker msgMaker(pfrom.GetCommonVersion());
+
+    LogPrint(BCLog::NET,
+             "more getheaders (%d) to end to peer=%d (startheight:%d)\n",
+             pindexLast->nHeight, pfrom.GetId(), peer.m_starting_height);
+    m_connman.PushMessage(
+        &pfrom, msgMaker.Make(NetMsgType::GETHEADERS,
+                              m_chainman.ActiveChain().GetLocator(pindexLast),
+                              uint256()));
+}
+
 void PeerManagerImpl::ProcessHeadersMessage(
     const Config &config, CNode &pfrom, Peer &peer,
     const std::vector<CBlockHeader> &headers, bool via_compact_block) {
@@ -3304,6 +3332,14 @@
 
     {
         LOCK(cs_main);
+
+        // Consider fetching more headers.
+        if (nCount == MAX_HEADERS_RESULTS) {
+            // Headers message had its maximum size; the peer may have more
+            // headers.
+            FetchMoreHeaders(pfrom, pindexLast, peer);
+        }
+
         CNodeState *nodestate = State(pfrom.GetId());
         if (nodestate->nUnconnectingHeaders > 0) {
             LogPrint(BCLog::NET,
@@ -3325,23 +3361,6 @@
             nodestate->m_last_block_announcement = GetTime();
         }
 
-        if (nCount == MAX_HEADERS_RESULTS) {
-            // Headers message had its maximum size; the peer may have more
-            // headers.
-            // TODO: optimize: if pindexLast is an ancestor of
-            // m_chainman.ActiveChain().Tip or m_chainman.m_best_header,
-            // continue from there instead.
-            LogPrint(
-                BCLog::NET,
-                "more getheaders (%d) to end to peer=%d (startheight:%d)\n",
-                pindexLast->nHeight, pfrom.GetId(), peer.m_starting_height);
-            m_connman.PushMessage(
-                &pfrom,
-                msgMaker.Make(NetMsgType::GETHEADERS,
-                              m_chainman.ActiveChain().GetLocator(pindexLast),
-                              uint256()));
-        }
-
         // If this set of headers is valid and ends in a block with at least as
         // much work as our tip, download as much as possible.
         if (CanDirectFetch() && pindexLast->IsValid(BlockValidity::TREE) &&