diff --git a/include/libtorrent/disk_io_thread.hpp b/include/libtorrent/disk_io_thread.hpp
index 37da2d310..d0c1d027e 100644
--- a/include/libtorrent/disk_io_thread.hpp
+++ b/include/libtorrent/disk_io_thread.hpp
@@ -388,6 +388,12 @@ namespace libtorrent
 			hasher_thread
 		};
 
+		enum
+		{
+			hasher_thread_mask = 3,
+			hasher_thread_divisor
+		};
+
 		void thread_fun(int thread_id, thread_type_t type
 			, boost::shared_ptr<io_service::work> w);
 
diff --git a/src/disk_io_thread.cpp b/src/disk_io_thread.cpp
index 79cf1c169..373d8e2dc 100644
--- a/src/disk_io_thread.cpp
+++ b/src/disk_io_thread.cpp
@@ -220,9 +220,8 @@ namespace libtorrent
 				boost::shared_ptr<io_service::work> work =
 					boost::make_shared<io_service::work>(boost::ref(m_ios));
 
-				// the magic number 3 is also used in add_job()
 				// every 4:th thread is a hasher thread
-				if ((thread_id & 0x3) == 3) type = hasher_thread;
+				if ((thread_id & hasher_thread_mask) == hasher_thread_mask) type = hasher_thread;
 				m_threads.push_back(boost::shared_ptr<thread>(
 					new thread(boost::bind(&disk_io_thread::thread_fun, this
 						, thread_id, type, work))));
@@ -3245,7 +3244,7 @@ namespace libtorrent
 		// if there are at least 3 threads, there's a hasher thread
 		// and the hash jobs go into a separate queue
 		// see set_num_threads()
-		if (m_num_threads > 3 && j->action == disk_io_job::hash)
+		if (m_num_threads > hasher_thread_mask && j->action == disk_io_job::hash)
 		{
 			m_queued_hash_jobs.push_back(j);
 		}
diff --git a/src/torrent.cpp b/src/torrent.cpp
index 2f7e02811..d7ff04bac 100644
--- a/src/torrent.cpp
+++ b/src/torrent.cpp
@@ -2770,8 +2770,11 @@ namespace {
 			/ m_torrent_file->piece_length();
 		// if we only keep a single read operation in-flight at a time, we suffer
 		// significant performance degradation. Always keep at least two jobs
-		// outstanding
-		if (num_outstanding < 2) num_outstanding = 2;
+		// outstanding per hasher thread
+		int const min_outstanding = 2
+			* std::max(1, settings().get_int(settings_pack::aio_threads)
+				/ disk_io_thread::hasher_thread_divisor);
+		if (num_outstanding < min_outstanding) num_outstanding = min_outstanding;
 
 		// we might already have some outstanding jobs, if we were paused and
 		// resumed quickly, before the outstanding jobs completed