diff --git a/lib/net/bip152.js b/lib/net/bip152.js
index 0de0d78a..17825183 100644
--- a/lib/net/bip152.js
+++ b/lib/net/bip152.js
@@ -50,7 +50,7 @@ function CompactBlock(options) {
   this.ptx = [];
 
   this.available = [];
-  this.idMap = {};
+  this.idMap = new Map();
   this.count = 0;
   this.sipKey = null;
   this.totalTX = 0;
@@ -322,7 +322,7 @@ CompactBlock.prototype.fillMempool = function fillMempool(witness, mempool) {
       hash = tx.witnessHash();
 
     id = this.sid(hash);
-    index = this.idMap[id];
+    index = this.idMap.get(id);
 
     if (index == null)
       continue;
@@ -445,10 +445,10 @@ CompactBlock.prototype.init = function init() {
     id = this.ids[i];
 
     // Fails on siphash collision
-    if (this.idMap[id])
+    if (this.idMap.has(id))
       return false;
 
-    this.idMap[id] = i + offset;
+    this.idMap.set(id, i + offset);
 
     // We're supposed to fail here if there's
     // more than 12 hash collisions, but we
diff --git a/lib/primitives/merkleblock.js b/lib/primitives/merkleblock.js
index 77ec81f2..8bf09227 100644
--- a/lib/primitives/merkleblock.js
+++ b/lib/primitives/merkleblock.js
@@ -106,7 +106,7 @@ MerkleBlock.prototype.refresh = function refresh(all) {
 MerkleBlock.prototype.addTX = function addTX(tx) {
   let tree = this.getTree();
   let hash = tx.hash('hex');
-  let index = tree.map[hash];
+  let index = tree.map.get(hash);
 
   this.txs.push(tx);
 
@@ -131,7 +131,7 @@ MerkleBlock.prototype.hasTX = function hasTX(hash) {
 
 MerkleBlock.prototype.indexOf = function indexOf(hash) {
   let tree = this.getTree();
-  let index = tree.map[hash];
+  let index = tree.map.get(hash);
 
   if (index == null)
     return -1;
@@ -140,8 +140,7 @@ MerkleBlock.prototype.indexOf = function indexOf(hash) {
 };
 
 /**
- * Verify the partial merkletree. Push leaves onto
- * {@link MerkleBlock#tx} and into {@link MerkleBlock#map}.
+ * Verify the partial merkletree.
  * @private
  * @returns {Boolean}
  */
@@ -152,8 +151,7 @@ MerkleBlock.prototype.verifyBody = function verifyBody() {
 };
 
 /**
- * Verify the partial merkletree. Push leaves onto
- * {@link MerkleBlock#tx} and into {@link MerkleBlock#map}.
+ * Verify the partial merkletree.
  * @private
  * @returns {Array} [valid, reason, score]
  */
@@ -196,7 +194,7 @@ MerkleBlock.prototype.extractTree = function extractTree() {
   let hashUsed = 0;
   let matches = [];
   let indexes = [];
-  let map = {};
+  let map = new Map();
   let failed = false;
   let hashes = this.hashes;
   let flags = this.flags;
@@ -232,7 +230,7 @@ MerkleBlock.prototype.extractTree = function extractTree() {
         let txid = hash.toString('hex');
         matches.push(hash);
         indexes.push(pos);
-        map[txid] = pos;
+        map.set(txid, pos);
       }
 
       return hash;
@@ -679,7 +677,7 @@ function PartialTree(root, matches, indexes, map) {
   this.root = root ? root.toString('hex') : encoding.NULL_HASH;
   this.matches = matches || [];
   this.indexes = indexes || [];
-  this.map = map || {};
+  this.map = map || new Map();
 }
 
 /*