diff --git a/include/libtorrent/peer_connection.hpp b/include/libtorrent/peer_connection.hpp
index 46fc87964..70a02c888 100644
--- a/include/libtorrent/peer_connection.hpp
+++ b/include/libtorrent/peer_connection.hpp
@@ -240,6 +240,9 @@ namespace aux {
 		http_seed
 	};
 
+	struct request_flags_tag;
+	using request_flags_t = flags::bitfield_flag<std::uint8_t, request_flags_tag>;
+
 	class TORRENT_EXTRA_EXPORT peer_connection
 		: public peer_connection_hot_members
 		, public bandwidth_socket
@@ -584,10 +587,12 @@ namespace aux {
 		// if the block was already time-critical, it returns false.
 		bool make_time_critical(piece_block const& block);
 
+		static constexpr request_flags_t time_critical{1};
+		static constexpr request_flags_t busy{2};
+
 		// adds a block to the request queue
 		// returns true if successful, false otherwise
-		enum flags_t { req_time_critical = 1, req_busy = 2 };
-		bool add_request(piece_block const& b, int flags = 0);
+		bool add_request(piece_block const& b, request_flags_t flags = {});
 
 		// clears the request queue and sends cancels for all messages
 		// in the download queue
diff --git a/src/peer_connection.cpp b/src/peer_connection.cpp
index 11de30242..ff3b35433 100644
--- a/src/peer_connection.cpp
+++ b/src/peer_connection.cpp
@@ -86,6 +86,9 @@ using namespace std::placeholders;
 
 namespace libtorrent {
 
+	constexpr request_flags_t peer_connection::time_critical;
+	constexpr request_flags_t peer_connection::busy;
+
 	namespace {
 
 	// the limits of the download queue size
@@ -3405,7 +3408,8 @@ namespace libtorrent {
 		return true;
 	}
 
-	bool peer_connection::add_request(piece_block const& block, int const flags)
+	bool peer_connection::add_request(piece_block const& block
+		, request_flags_t const flags)
 	{
 		TORRENT_ASSERT(is_single_thread());
 		INVARIANT_CHECK;
@@ -3446,7 +3450,7 @@ namespace libtorrent {
 			return false;
 		}
 
-		if ((flags & req_busy) && !(flags & req_time_critical))
+		if ((flags & busy) && !(flags & time_critical))
 		{
 			// this block is busy (i.e. it has been requested
 			// from another peer already). Only allow one busy
@@ -3495,8 +3499,8 @@ namespace libtorrent {
 		}
 
 		pending_block pb(block);
-		pb.busy = (flags & req_busy) ? true : false;
-		if (flags & req_time_critical)
+		pb.busy = (flags & busy) ? true : false;
+		if (flags & time_critical)
 		{
 			m_request_queue.insert(m_request_queue.begin() + m_queued_time_critical
 				, pb);
diff --git a/src/request_blocks.cpp b/src/request_blocks.cpp
index 324ca3a02..c6c27e0af 100644
--- a/src/request_blocks.cpp
+++ b/src/request_blocks.cpp
@@ -252,7 +252,7 @@ namespace libtorrent {
 			// ok, we found a piece that's not being downloaded
 			// by somebody else. request it from this peer
 			// and return
-			if (!c.add_request(*i, 0)) continue;
+			if (!c.add_request(*i, {})) continue;
 			TORRENT_ASSERT(p.num_peers(*i) == 1);
 			TORRENT_ASSERT(p.is_requested(*i));
 			num_requests--;
@@ -298,7 +298,7 @@ namespace libtorrent {
 		TORRENT_ASSERT(!p.is_finished(busy_block));
 		TORRENT_ASSERT(p.num_peers(busy_block) > 0);
 
-		c.add_request(busy_block, peer_connection::req_busy);
+		c.add_request(busy_block, peer_connection::busy);
 		return true;
 	}
 
diff --git a/src/torrent.cpp b/src/torrent.cpp
index d54f547df..33d90b6cd 100644
--- a/src/torrent.cpp
+++ b/src/torrent.cpp
@@ -9643,8 +9643,8 @@ namespace libtorrent {
 			}
 			else
 			{
-				if (!c.add_request(b, peer_connection::req_time_critical
-					| (busy_mode ? peer_connection::req_busy : 0)))
+				if (!c.add_request(b, peer_connection::time_critical
+					| (busy_mode ? peer_connection::busy : request_flags_t{})))
 				{
 #if TORRENT_DEBUG_STREAMING > 1
 					std::printf("failed to request block [%d, %d]\n"