diff --git a/lib/bcoin/txdb.js b/lib/bcoin/txdb.js
index ce76c119..db1960c1 100644
--- a/lib/bcoin/txdb.js
+++ b/lib/bcoin/txdb.js
@@ -255,6 +255,7 @@ function TXDB(wallet) {
   this.logger = wallet.db.logger;
   this.network = wallet.db.network;
   this.options = wallet.db.options;
+  this.locked = {};
 
   this.locker = new bcoin.locker(this);
   this.coinCache = new bcoin.lru(10000, 1);
@@ -808,6 +809,9 @@ TXDB.prototype.add = function add(tx, info, callback) {
             if (err)
               return callback(err);
 
+            // Clear any locked coins to free up memory.
+            self.unlockTX(tx);
+
             self.emit('tx', tx, info);
 
             if (tx.ts !== 0)
@@ -1000,6 +1004,9 @@ TXDB.prototype._confirm = function _confirm(tx, info, callback) {
     // and remove pending flag to mark as confirmed.
     assert(tx.height >= 0);
 
+    // Clear any locked coins to free up memory.
+    self.unlockTX(tx);
+
     // Save the original received time.
     tx.ps = existing.ps;
 
@@ -1308,6 +1315,90 @@ TXDB.prototype._unconfirm = function unconfirm(tx, info, callback, force) {
   });
 };
 
+/**
+ * Lock all coins in a transaction.
+ * @param {TX} tx
+ */
+
+TXDB.prototype.lockTX = function lockTX(tx) {
+  var i, input;
+
+  if (tx.isCoinbase())
+    return;
+
+  for (i = 0; i < tx.inputs.length; i++) {
+    input = tx.inputs[i];
+    this.lockCoin(input.prevout);
+  }
+};
+
+/**
+ * Unlock all coins in a transaction.
+ * @param {TX} tx
+ */
+
+TXDB.prototype.unlockTX = function unlockTX(tx) {
+  var i, input;
+
+  if (tx.isCoinbase())
+    return;
+
+  for (i = 0; i < tx.inputs.length; i++) {
+    input = tx.inputs[i];
+    this.unlockCoin(input.prevout);
+  }
+};
+
+/**
+ * Lock a single coin.
+ * @param {Coin|Outpoint} coin
+ */
+
+TXDB.prototype.lockCoin = function lockCoin(coin) {
+  var key = coin.hash + coin.index;
+  this.locked[key] = true;
+};
+
+/**
+ * Unlock a single coin.
+ * @param {Coin|Outpoint} coin
+ */
+
+TXDB.prototype.unlockCoin = function unlockCoin(coin) {
+  var key = coin.hash + coin.index;
+  delete this.locked[key];
+};
+
+/**
+ * Test locked status of a single coin.
+ * @param {Coin|Outpoint} coin
+ */
+
+TXDB.prototype.isLocked = function isLocked(coin) {
+  var key = coin.hash + coin.index;
+  return this.locked[key] === true;
+};
+
+/**
+ * Filter array of coins or outpoints
+ * for only unlocked ones.
+ * @param {Coin[]|Outpoint[]}
+ * @returns {Array}
+ */
+
+TXDB.prototype.filterLocked = function filterLocked(coins) {
+  var out = [];
+  var i, coin;
+
+  for (i = 0; i < coins.length; i++) {
+    coin = coins[i];
+    if (!this.isLocked(coin))
+      out.push(coins);
+  }
+
+  return coins;
+};
+
 /**
  * Get hashes of all transactions in the database.
  * @param {Number?} account
diff --git a/lib/bcoin/wallet.js b/lib/bcoin/wallet.js
index 13e6e332..cec5e666 100644
--- a/lib/bcoin/wallet.js
+++ b/lib/bcoin/wallet.js
@@ -815,6 +815,9 @@ Wallet.prototype.fund = function fund(tx, options, callback, force) {
           rate = self.network.getRate();
       }
 
+      // Don't use any locked coins.
+      coins = self.tx.filterLocked(coins);
+
       try {
         tx.fund(coins, {
           selection: options.selection || 'age',
@@ -2053,8 +2056,6 @@ function Account(db, options) {
   if (!(this instanceof Account))
     return new Account(db, options);
 
-  EventEmitter.call(this);
-
   assert(db, 'Database is required.');
 
   this.db = db;
@@ -2082,8 +2083,6 @@ function Account(db, options) {
     this.fromOptions(options);
 }
 
-utils.inherits(Account, EventEmitter);
-
 /**
  * Inject properties from options object.
  * @private