diff --git a/lib/services/address/index.js b/lib/services/address/index.js
index 4da9f46d..2592b842 100644
--- a/lib/services/address/index.js
+++ b/lib/services/address/index.js
@@ -451,7 +451,7 @@ AddressService.prototype._getAddressHistory = function(address, options, callbac
       if (mempoolTxs.length <= 0) {
         return next();
       }
-      async.mapSeries(mempoolTxs, 4, function(tx, next) {
+      async.mapSeries(mempoolTxs, function(tx, next) {
         self._transaction.setTxMetaInfo(tx, options, next);
       }, function(err, txs) {
         if (err) {