diff --git a/lib/blockchain/chain.js b/lib/blockchain/chain.js
index f895074b..533b9cc8 100644
--- a/lib/blockchain/chain.js
+++ b/lib/blockchain/chain.js
@@ -9,20 +9,20 @@
 
 const assert = require('assert');
 const path = require('path');
+const Logger = require('blgr');
+const {Lock} = require('bmutex');
+const encoding = require('bbuf/lib/encoding');
 const AsyncEmitter = require('../utils/asyncemitter');
 const Network = require('../protocol/network');
-const Logger = require('blgr');
 const ChainDB = require('./chaindb');
 const common = require('./common');
 const consensus = require('../protocol/consensus');
 const util = require('../utils/util');
-const Lock = require('../utils/lock');
 const LRU = require('../utils/lru');
 const ChainEntry = require('./chainentry');
 const CoinView = require('../coins/coinview');
 const Script = require('../script/script');
 const {VerifyError} = require('../protocol/errors');
-const encoding = require('bbuf/lib/encoding');
 const thresholdStates = common.thresholdStates;
 
 /**
diff --git a/lib/mining/cpuminer.js b/lib/mining/cpuminer.js
index 5a4cebb6..a44c8c3d 100644
--- a/lib/mining/cpuminer.js
+++ b/lib/mining/cpuminer.js
@@ -9,10 +9,10 @@
 
 const assert = require('assert');
 const EventEmitter = require('events');
+const {Lock} = require('bmutex');
+const encoding = require('bbuf/lib/encoding');
 const util = require('../utils/util');
 const mine = require('./mine');
-const Lock = require('../utils/lock');
-const encoding = require('bbuf/lib/encoding');
 
 /**
  * CPU miner.
diff --git a/lib/net/peer.js b/lib/net/peer.js
index ae475074..60eb0770 100644
--- a/lib/net/peer.js
+++ b/lib/net/peer.js
@@ -9,6 +9,7 @@
 
 const assert = require('assert');
 const EventEmitter = require('events');
+const {Lock} = require('bmutex');
 const {format} = require('util');
 const tcp = require('btcp');
 const Logger = require('blgr');
@@ -20,7 +21,6 @@ const packets = require('./packets');
 const consensus = require('../protocol/consensus');
 const common = require('./common');
 const InvItem = require('../primitives/invitem');
-const Lock = require('../utils/lock');
 const BIP151 = require('./bip151');
 const BIP150 = require('./bip150');
 const BIP152 = require('./bip152');
diff --git a/lib/net/pool.js b/lib/net/pool.js
index 66564863..8315404a 100644
--- a/lib/net/pool.js
+++ b/lib/net/pool.js
@@ -9,6 +9,7 @@
 
 const assert = require('assert');
 const EventEmitter = require('events');
+const {Lock} = require('bmutex');
 const IP = require('binet');
 const dns = require('bdns');
 const tcp = require('btcp');
@@ -25,7 +26,6 @@ const Address = require('../primitives/address');
 const BIP150 = require('./bip150');
 const BIP151 = require('./bip151');
 const BIP152 = require('./bip152');
-const Lock = require('../utils/lock');
 const Network = require('../protocol/network');
 const Peer = require('./peer');
 const external = require('./external');
diff --git a/lib/node/rpc.js b/lib/node/rpc.js
index 5423d5a5..0aecc18c 100644
--- a/lib/node/rpc.js
+++ b/lib/node/rpc.js
@@ -8,12 +8,16 @@
 
 const assert = require('assert');
 const bweb = require('bweb');
-const util = require('../utils/util');
+const {Lock} = require('bmutex');
+const IP = require('binet');
 const hash160 = require('bcrypto/lib/hash160');
 const hash256 = require('bcrypto/lib/hash256');
 const ccmp = require('bcrypto/lib/ccmp');
-const common = require('../blockchain/common');
 const secp256k1 = require('bcrypto/lib/secp256k1');
+const encoding = require('bbuf/lib/encoding');
+const Validator = require('bval/lib/validator');
+const util = require('../utils/util');
+const common = require('../blockchain/common');
 const Amount = require('../btc/amount');
 const NetAddress = require('../primitives/netaddress');
 const Script = require('../script/script');
@@ -28,12 +32,8 @@ const Network = require('../protocol/network');
 const Outpoint = require('../primitives/outpoint');
 const Output = require('../primitives/output');
 const TX = require('../primitives/tx');
-const IP = require('binet');
-const encoding = require('bbuf/lib/encoding');
 const consensus = require('../protocol/consensus');
-const Validator = require('bval/lib/validator');
 const pkg = require('../pkg');
-const Lock = require('../utils/lock');
 const RPCBase = bweb.RPC;
 const RPCError = bweb.RPCError;
 
diff --git a/lib/node/spvnode.js b/lib/node/spvnode.js
index 8da0137e..613ae2cb 100644
--- a/lib/node/spvnode.js
+++ b/lib/node/spvnode.js
@@ -8,7 +8,7 @@
 'use strict';
 
 const assert = require('assert');
-const Lock = require('../utils/lock');
+const {Lock} = require('bmutex');
 const Chain = require('../blockchain/chain');
 const Pool = require('../net/pool');
 const Node = require('./node');
diff --git a/lib/utils/index.js b/lib/utils/index.js
index 4f8aa8fd..39d63224 100644
--- a/lib/utils/index.js
+++ b/lib/utils/index.js
@@ -15,7 +15,5 @@ exports.binary = require('./binary');
 exports.fixed = require('./fixed');
 exports.Heap = require('./heap');
 exports.List = require('./list');
-exports.Lock = require('./lock');
 exports.LRU = require('./lru');
-exports.MappedLock = require('./mappedlock');
 exports.util = require('./util');
diff --git a/lib/utils/lock.js b/lib/utils/lock.js
deleted file mode 100644
index 688604aa..00000000
--- a/lib/utils/lock.js
+++ /dev/null
@@ -1,215 +0,0 @@
-/*!
- * lock.js - lock and queue for bcoin
- * Copyright (c) 2014-2015, Fedor Indutny (MIT License)
- * Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
- * https://github.com/bcoin-org/bcoin
- */
-
-'use strict';
-
-const assert = require('assert');
-
-/**
- * Mutex Lock
- * @alias module:utils.Lock
- */
-
-class Lock {
-  /**
-   * Create a lock.
-   * @constructor
-   * @param {Boolean?} named - Whether to
-   * maintain a map of queued jobs by job name.
-   */
-
-  constructor(named = false) {
-    this.named = named === true;
-
-    this.jobs = [];
-    this.busy = false;
-    this.destroyed = false;
-
-    this.map = new Map();
-    this.current = null;
-
-    this.unlocker = this.unlock.bind(this);
-  }
-
-  /**
-   * Create a closure scoped lock.
-   * @param {Boolean?} named
-   * @returns {Function} Lock method.
-   */
-
-  static create(named) {
-    const lock = new Lock(named);
-    return function _lock(arg1, arg2) {
-      return lock.lock(arg1, arg2);
-    };
-  }
-
-  /**
-   * Test whether the lock has a pending
-   * job or a job in progress (by name).
-   * @param {String} name
-   * @returns {Boolean}
-   */
-
-  has(name) {
-    assert(this.named, 'Must use named jobs.');
-
-    if (this.current === name)
-      return true;
-
-    return this.pending(name);
-  }
-
-  /**
-   * Test whether the lock has
-   * a pending job by name.
-   * @param {String} name
-   * @returns {Boolean}
-   */
-
-  pending(name) {
-    assert(this.named, 'Must use named jobs.');
-
-    const count = this.map.get(name);
-
-    if (count == null)
-      return false;
-
-    return count > 0;
-  }
-
-  /**
-   * Lock the parent object and all its methods
-   * which use the lock. Begin to queue calls.
-   * @param {String?} name - Job name.
-   * @param {Boolean?} force - Bypass the lock.
-   * @returns {Promise} - Returns {Function}, must be
-   * called once the method finishes executing in order
-   * to resolve the queue.
-   */
-
-  lock(arg1, arg2) {
-    let name, force;
-
-    if (this.named) {
-      name = arg1 || null;
-      force = arg2 || false;
-    } else {
-      name = null;
-      force = arg1 || false;
-    }
-
-    if (this.destroyed)
-      return Promise.reject(new Error('Lock is destroyed.'));
-
-    if (force) {
-      assert(this.busy);
-      return Promise.resolve(nop);
-    }
-
-    if (this.busy) {
-      if (name) {
-        const count = this.map.get(name) || 0;
-        this.map.set(name, count + 1);
-      }
-      return new Promise((resolve, reject) => {
-        this.jobs.push(new Job(resolve, reject, name));
-      });
-    }
-
-    this.busy = true;
-    this.current = name;
-
-    return Promise.resolve(this.unlocker);
-  }
-
-  /**
-   * The actual unlock callback.
-   * @private
-   */
-
-  unlock() {
-    assert(this.destroyed || this.busy);
-
-    this.busy = false;
-    this.current = null;
-
-    if (this.jobs.length === 0)
-      return;
-
-    assert(!this.destroyed);
-
-    const job = this.jobs.shift();
-
-    if (job.name) {
-      let count = this.map.get(job.name);
-      assert(count > 0);
-      if (--count === 0)
-        this.map.delete(job.name);
-      else
-        this.map.set(job.name, count);
-    }
-
-    this.busy = true;
-    this.current = job.name;
-
-    job.resolve(this.unlocker);
-  }
-
-  /**
-   * Destroy the lock. Purge all pending calls.
-   */
-
-  destroy() {
-    assert(!this.destroyed, 'Lock is already destroyed.');
-
-    this.destroyed = true;
-
-    const jobs = this.jobs;
-
-    this.busy = false;
-    this.jobs = [];
-    this.map.clear();
-    this.current = null;
-
-    for (const job of jobs)
-      job.reject(new Error('Lock was destroyed.'));
-  }
-}
-
-/**
- * Lock Job
- * @ignore
- */
-
-class Job {
-  /**
-   * Create a lock job.
-   * @constructor
-   * @param {Function} resolve
-   * @param {Function} reject
-   * @param {String?} name
-   */
-
-  constructor(resolve, reject, name) {
-    this.resolve = resolve;
-    this.reject = reject;
-    this.name = name || null;
-  }
-}
-
-/*
- * Helpers
- */
-
-function nop() {}
-
-/*
- * Expose
- */
-
-module.exports = Lock;
diff --git a/lib/utils/mappedlock.js b/lib/utils/mappedlock.js
deleted file mode 100644
index d3673af3..00000000
--- a/lib/utils/mappedlock.js
+++ /dev/null
@@ -1,181 +0,0 @@
-/*!
- * mappedlock.js - lock and queue for bcoin
- * Copyright (c) 2014-2015, Fedor Indutny (MIT License)
- * Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
- * https://github.com/bcoin-org/bcoin
- */
-
-'use strict';
-
-const assert = require('assert');
-
-/**
- * Mapped Lock
- * @alias module:utils.MappedLock
- */
-
-class MappedLock {
-  /**
-   * Create a mapped lock.
-   * @constructor
-   */
-
-  constructor() {
-    this.jobs = new Map();
-    this.busy = new Set();
-    this.destroyed = false;
-  }
-
-  /**
-   * Create a closure scoped lock.
-   * @returns {Function} Lock method.
-   */
-
-  static create() {
-    const lock = new MappedLock();
-    return function _lock(key, force) {
-      return lock.lock(key, force);
-    };
-  }
-
-  /**
-   * Test whether the lock has a pending
-   * job or a job in progress (by name).
-   * @param {String} name
-   * @returns {Boolean}
-   */
-
-  has(name) {
-    return this.busy.has(name);
-  }
-
-  /**
-   * Test whether the lock has
-   * a pending job by name.
-   * @param {String} name
-   * @returns {Boolean}
-   */
-
-  pending(name) {
-    return this.jobs.has(name);
-  }
-
-  /**
-   * Lock the parent object and all its methods
-   * which use the lock with a specified key.
-   * Begin to queue calls.
-   * @param {String|Number} key
-   * @param {Boolean} [force=false] - Force a call.
-   * @returns {Promise} - Returns {Function}, must be
-   * called once the method finishes executing in order
-   * to resolve the queue.
-   */
-
-  lock(key, force = false) {
-    if (this.destroyed)
-      return Promise.reject(new Error('Lock is destroyed.'));
-
-    if (key == null)
-      return Promise.resolve(nop);
-
-    if (force) {
-      assert(this.busy.has(key));
-      return Promise.resolve(nop);
-    }
-
-    if (this.busy.has(key)) {
-      return new Promise((resolve, reject) => {
-        if (!this.jobs.has(key))
-          this.jobs.set(key, []);
-        this.jobs.get(key).push(new Job(resolve, reject));
-      });
-    }
-
-    this.busy.add(key);
-
-    return Promise.resolve(this.unlock(key));
-  }
-
-  /**
-   * Create an unlock callback.
-   * @private
-   * @param {String} key
-   * @returns {Function} Unlocker.
-   */
-
-  unlock(key) {
-    const self = this;
-    return function unlocker() {
-      const jobs = self.jobs.get(key);
-
-      assert(self.destroyed || self.busy.has(key));
-      self.busy.delete(key);
-
-      if (!jobs)
-        return;
-
-      assert(!self.destroyed);
-
-      const job = jobs.shift();
-      assert(job);
-
-      if (jobs.length === 0)
-        self.jobs.delete(key);
-
-      self.busy.add(key);
-
-      job.resolve(unlocker);
-    };
-  }
-
-  /**
-   * Destroy the lock. Purge all pending calls.
-   */
-
-  destroy() {
-    assert(!this.destroyed, 'Lock is already destroyed.');
-
-    const map = this.jobs;
-
-    this.destroyed = true;
-
-    this.jobs = new Map();
-    this.busy = new Map();
-
-    for (const jobs of map.values()) {
-      for (const job of jobs)
-        job.reject(new Error('Lock was destroyed.'));
-    }
-  }
-}
-
-/**
- * Lock Job
- * @ignore
- */
-
-class Job {
-  /**
-   * Create a lock job.
-   * @constructor
-   * @param {Function} resolve
-   * @param {Function} reject
-   */
-
-  constructor(resolve, reject) {
-    this.resolve = resolve;
-    this.reject = reject;
-  }
-}
-
-/*
- * Helpers
- */
-
-function nop() {}
-
-/*
- * Expose
- */
-
-module.exports = MappedLock;
diff --git a/lib/wallet/masterkey.js b/lib/wallet/masterkey.js
index 2a72bf5f..7fed5965 100644
--- a/lib/wallet/masterkey.js
+++ b/lib/wallet/masterkey.js
@@ -7,9 +7,7 @@
 'use strict';
 
 const assert = require('assert');
-const Network = require('../protocol/network');
-const util = require('../utils/util');
-const Lock = require('../utils/lock');
+const {Lock} = require('bmutex');
 const random = require('bcrypto/lib/random');
 const cleanse = require('bcrypto/lib/cleanse');
 const aes = require('bcrypto/lib/aes');
@@ -19,6 +17,8 @@ const scrypt = require('bcrypto/lib/scrypt');
 const BufferReader = require('bbuf/lib/reader');
 const StaticWriter = require('bbuf/lib/staticwriter');
 const encoding = require('bbuf/lib/encoding');
+const Network = require('../protocol/network');
+const util = require('../utils/util');
 const HD = require('../hd/hd');
 const Mnemonic = HD.Mnemonic;
 
diff --git a/lib/wallet/rpc.js b/lib/wallet/rpc.js
index 3bbba6fd..e05e76a1 100644
--- a/lib/wallet/rpc.js
+++ b/lib/wallet/rpc.js
@@ -7,11 +7,14 @@
 'use strict';
 
 const assert = require('assert');
-const bweb = require('bweb');
-const fs = require('bfile');
 const {format} = require('util');
-const util = require('../utils/util');
+const bweb = require('bweb');
+const {Lock} = require('bmutex');
+const fs = require('bfile');
 const hash256 = require('bcrypto/lib/hash256');
+const encoding = require('bbuf/lib/encoding');
+const Validator = require('bval/lib/validator');
+const util = require('../utils/util');
 const Amount = require('../btc/amount');
 const Script = require('../script/script');
 const Address = require('../primitives/address');
@@ -21,10 +24,7 @@ const MTX = require('../primitives/mtx');
 const Outpoint = require('../primitives/outpoint');
 const Output = require('../primitives/output');
 const TX = require('../primitives/tx');
-const encoding = require('bbuf/lib/encoding');
 const pkg = require('../pkg');
-const Validator = require('bval/lib/validator');
-const Lock = require('../utils/lock');
 const common = require('./common');
 const RPCBase = bweb.RPC;
 const RPCError = bweb.RPCError;
diff --git a/lib/wallet/wallet.js b/lib/wallet/wallet.js
index 6606935e..edec74cd 100644
--- a/lib/wallet/wallet.js
+++ b/lib/wallet/wallet.js
@@ -9,15 +9,15 @@
 
 const assert = require('assert');
 const EventEmitter = require('events');
-const Network = require('../protocol/network');
+const {Lock} = require('bmutex');
 const encoding = require('bbuf/lib/encoding');
-const Lock = require('../utils/lock');
 const hash160 = require('bcrypto/lib/hash160');
 const hash256 = require('bcrypto/lib/hash256');
 const cleanse = require('bcrypto/lib/cleanse');
 const BufferReader = require('bbuf/lib/reader');
 const StaticWriter = require('bbuf/lib/staticwriter');
 const base58 = require('bstr/lib/base58');
+const Network = require('../protocol/network');
 const TXDB = require('./txdb');
 const Path = require('./path');
 const common = require('./common');
diff --git a/lib/wallet/walletdb.js b/lib/wallet/walletdb.js
index 96e4d797..3a6e9480 100644
--- a/lib/wallet/walletdb.js
+++ b/lib/wallet/walletdb.js
@@ -10,6 +10,8 @@
 const assert = require('assert');
 const path = require('path');
 const EventEmitter = require('events');
+const Lock = require('bmutex/lib/lock');
+const MapLock = require('bmutex/lib/maplock');
 const BDB = require('bdb');
 const Logger = require('blgr');
 const encoding = require('bbuf/lib/encoding');
@@ -17,8 +19,6 @@ const ccmp = require('bcrypto/lib/ccmp');
 const aes = require('bcrypto/lib/aes');
 const BloomFilter = require('bfilter/lib/bloom');
 const StaticWriter = require('bbuf/lib/staticwriter');
-const Lock = require('../utils/lock');
-const MappedLock = require('../utils/mappedlock');
 const Network = require('../protocol/network');
 const Path = require('./path');
 const common = require('./common');
@@ -65,7 +65,7 @@ function WalletDB(options) {
   this.rescanning = false;
 
   // Wallet read lock.
-  this.readLock = new MappedLock();
+  this.readLock = new MapLock();
 
   // Wallet write lock (creation and rename).
   this.writeLock = new Lock();
diff --git a/package.json b/package.json
index 4d875a90..830a429d 100644
--- a/package.json
+++ b/package.json
@@ -30,6 +30,7 @@
     "bfile": "^0.0.1",
     "bfilter": "^0.0.1",
     "binet": "^0.0.1",
+    "bmutex": "^0.0.1",
     "breq": "^0.0.1",
     "bsock": "^0.0.1",
     "bstr": "^0.0.1",