diff --git a/lib/http/rpc.js b/lib/http/rpc.js
index a9166591..ff1e5090 100644
--- a/lib/http/rpc.js
+++ b/lib/http/rpc.js
@@ -862,7 +862,8 @@ RPC.prototype.getTXOutProof = async function getTXOutProof(args, help) {
     throw new RPCError(errs.INVALID_PARAMETER, 'Invalid TXIDs.');
 
   const items = new Validator([txids]);
-  const hashes = new Set();
+  const set = new Set();
+  const hashes = [];
 
   let last = null;
 
@@ -872,10 +873,11 @@ RPC.prototype.getTXOutProof = async function getTXOutProof(args, help) {
     if (!hash)
       throw new RPCError(errs.TYPE_ERROR, 'Invalid TXID.');
 
-    if (hashes.has(hash))
+    if (set.has(hash))
       throw new RPCError(errs.INVALID_PARAMETER, 'Duplicate txid.');
 
-    hashes.add(hash);
+    set.add(hash);
+    hashes.push(hash);
 
     last = hash;
   }
@@ -897,14 +899,14 @@ RPC.prototype.getTXOutProof = async function getTXOutProof(args, help) {
   if (!block)
     throw new RPCError(errs.MISC_ERROR, 'Block not found.');
 
-  for (const txid of hashes) {
-    if (!block.hasTX(txid)) {
+  for (const hash of hashes) {
+    if (!block.hasTX(hash)) {
       throw new RPCError(errs.VERIFY_ERROR,
         'Block does not contain all txids.');
     }
   }
 
-  block = MerkleBlock.fromHashes(block, txids);
+  block = MerkleBlock.fromHashes(block, hashes);
 
   return block.toRaw().toString('hex');
 };