diff --git a/src/cpp/ripple/OrderBookDB.cpp b/src/cpp/ripple/OrderBookDB.cpp
index 2aed79cf8..619ae87b4 100644
--- a/src/cpp/ripple/OrderBookDB.cpp
+++ b/src/cpp/ripple/OrderBookDB.cpp
@@ -77,7 +77,7 @@ void OrderBookDB::setup(Ledger::ref ledger)
 std::vector<OrderBook::pointer>& OrderBookDB::getBooks(const uint160& issuerID)
 {
 	boost::recursive_mutex::scoped_lock sl(mLock);
-	std::map< uint160, std::vector<OrderBook::pointer> >::iterator it = mIssuerMap.find(issuerID);
+	boost::unordered_map< uint160, std::vector<OrderBook::pointer> >::iterator it = mIssuerMap.find(issuerID);
 	return (it == mIssuerMap.end())
 		? mEmptyVector
 		: it->second;
@@ -87,7 +87,7 @@ std::vector<OrderBook::pointer>& OrderBookDB::getBooks(const uint160& issuerID)
 void OrderBookDB::getBooks(const uint160& issuerID, const uint160& currencyID, std::vector<OrderBook::pointer>& bookRet)
 {
 	boost::recursive_mutex::scoped_lock sl(mLock);
-	std::map< uint160, std::vector<OrderBook::pointer> >::iterator it = mIssuerMap.find(issuerID);
+	boost::unordered_map< uint160, std::vector<OrderBook::pointer> >::iterator it = mIssuerMap.find(issuerID);
 	if (it != mIssuerMap.end())
 	{
 		BOOST_FOREACH(OrderBook::ref book, it->second)
diff --git a/src/cpp/ripple/OrderBookDB.h b/src/cpp/ripple/OrderBookDB.h
index c3b99fda4..5563b2e3e 100644
--- a/src/cpp/ripple/OrderBookDB.h
+++ b/src/cpp/ripple/OrderBookDB.h
@@ -2,9 +2,11 @@
 #ifndef ORDERBOOK_DB_H
 #define ORDERBOOK_DB_H
 
+#include <boost/shared_ptr.hpp>
+#include <boost/unordered_map.hpp>
+
 #include "Ledger.h"
 #include "OrderBook.h"
-#include <boost/shared_ptr.hpp>
 
 
 //
@@ -27,7 +29,7 @@ class OrderBookDB
 {
 	std::vector<OrderBook::pointer> mEmptyVector;
 	std::vector<OrderBook::pointer> mXRPOrders;
-	std::map<uint160, std::vector<OrderBook::pointer> > mIssuerMap;
+	boost::unordered_map<uint160, std::vector<OrderBook::pointer> > mIssuerMap;
 	//std::vector<OrderBook::pointer> mAllOrderBooks;
 
 	// issuerIn, issuerOut, currencyIn, currencyOut