diff --git a/lib/net/pool.js b/lib/net/pool.js
index e885871c..8e4ea2e3 100644
--- a/lib/net/pool.js
+++ b/lib/net/pool.js
@@ -1830,7 +1830,7 @@ Pool.prototype._handleTX = co(function* handleTX(peer, packet) {
     if (peer.merkleBlock.hasTX(tx)) {
       peer.merkleBlock.addTX(tx);
       if (--peer.merkleMatches === 0) {
-        yield this.addBlock(peer, peer.merkleBlock);
+        yield this._addBlock(peer, peer.merkleBlock);
         peer.merkleTime = -1;
         peer.merkleBlock = null;
         peer.merkleMatches = 0;
@@ -1993,6 +1993,22 @@ Pool.prototype.handleFilterClear = co(function* handleFilterClear(peer, packet)
  */
 
 Pool.prototype.handleMerkleBlock = co(function* handleMerkleBlock(peer, packet) {
+  var unlock = yield this.locker.lock();
+  try {
+    return yield this._handleMerkleBlock(peer, packet);
+  } finally {
+    unlock();
+  }
+});
+
+/**
+ * Handle `merkleblock` packet (without a lock).
+ * @private
+ * @param {Peer} peer
+ * @param {MerkleBlockPacket} block
+ */
+
+Pool.prototype._handleMerkleBlock = co(function* handleMerkleBlock(peer, packet) {
   var block = packet.block;
   var hash = block.hash('hex');
 
@@ -2033,7 +2049,7 @@ Pool.prototype.handleMerkleBlock = co(function* handleMerkleBlock(peer, packet)
   }
 
   if (block.matches.length === 0) {
-    yield this.addBlock(peer, block);
+    yield this._addBlock(peer, block);
     return;
   }