diff --git a/lib/blockchain/chain.js b/lib/blockchain/chain.js
index f4c19621..232e963b 100644
--- a/lib/blockchain/chain.js
+++ b/lib/blockchain/chain.js
@@ -548,7 +548,7 @@ Chain.prototype.verifyDuplicates = async function verifyDuplicates(block, prev,
 
   // Check all transactions.
   for (let tx of block.txs) {
-    let result = await this.db.hasCoins(tx.hash());
+    let result = await this.db.hasCoins(tx);
 
     if (result) {
       let height = prev.height + 1;
diff --git a/lib/blockchain/chaindb.js b/lib/blockchain/chaindb.js
index 8b5828b7..dbe2e0d7 100644
--- a/lib/blockchain/chaindb.js
+++ b/lib/blockchain/chaindb.js
@@ -894,22 +894,17 @@ ChainDB.prototype.getCoin = async function getCoin(hash, index) {
 /**
  * Check whether coins are still unspent. Necessary for bip30.
  * @see https://bitcointalk.org/index.php?topic=67738.0
- * @param {Hash} hash
+ * @param {TX} tx
  * @returns {Promise} - Returns Boolean.
  */
 
-ChainDB.prototype.hasCoins = async function hasCoins(hash) {
-  let iter = this.db.iterator({
-    gte: layout.c(hash, 0x00000000),
-    lte: layout.c(hash, 0xffffffff)
-  });
-
-  if (!(await iter.next()))
-    return false;
-
-  await iter.end();
-
-  return true;
+ChainDB.prototype.hasCoins = async function hasCoins(tx) {
+  for (let i = 0; i < tx.outputs.length; i++) {
+    let key = layout.c(tx.hash(), i);
+    if (await this.db.has(key))
+      return true;
+  }
+  return false;
 };
 
 /**
diff --git a/lib/mempool/mempool.js b/lib/mempool/mempool.js
index 384fbc7a..ff7804b1 100644
--- a/lib/mempool/mempool.js
+++ b/lib/mempool/mempool.js
@@ -803,7 +803,7 @@ Mempool.prototype.insertTX = async function insertTX(tx, id) {
   // We can test whether this is an
   // non-fully-spent transaction on
   // the chain.
-  if (await this.chain.db.hasCoins(hash)) {
+  if (await this.chain.db.hasCoins(tx)) {
     throw new VerifyError(tx,
       'alreadyknown',
       'txn-already-known',