diff --git a/include/libtorrent/alert.hpp b/include/libtorrent/alert.hpp
index d6dfbd886..4dbb496ab 100644
--- a/include/libtorrent/alert.hpp
+++ b/include/libtorrent/alert.hpp
@@ -68,8 +68,7 @@ POSSIBILITY OF SUCH DAMAGE.
 namespace libtorrent {
 
 	// hidden
-	struct alert_category_tag;
-	using alert_category_t = flags::bitfield_flag<std::uint32_t, alert_category_tag>;
+	using alert_category_t = flags::bitfield_flag<std::uint32_t, struct alert_category_tag>;
 
 	// The ``alert`` class is the base class that specific messages are derived from.
 	// alert types are not copyable, and cannot be constructed by the client. The
diff --git a/include/libtorrent/alert_types.hpp b/include/libtorrent/alert_types.hpp
index 89c80041f..bffd136f4 100644
--- a/include/libtorrent/alert_types.hpp
+++ b/include/libtorrent/alert_types.hpp
@@ -2552,8 +2552,7 @@ namespace libtorrent {
 	};
 
 	// hidden
-	struct picker_flags_tag;
-	using picker_flags_t = flags::bitfield_flag<std::uint32_t, picker_flags_tag>;
+	using picker_flags_t = flags::bitfield_flag<std::uint32_t, struct picker_flags_tag>;
 
 	// this is posted when one or more blocks are picked by the piece picker,
 	// assuming the verbose piece picker logging is enabled (see
diff --git a/include/libtorrent/aux_/escape_string.hpp b/include/libtorrent/aux_/escape_string.hpp
index 74e255d91..5007df460 100644
--- a/include/libtorrent/aux_/escape_string.hpp
+++ b/include/libtorrent/aux_/escape_string.hpp
@@ -42,8 +42,7 @@ POSSIBILITY OF SUCH DAMAGE.
 namespace libtorrent {
 
 	// hidden
-	struct encode_string_flags_tag;
-	using encode_string_flags_t = flags::bitfield_flag<std::uint8_t, encode_string_flags_tag>;
+	using encode_string_flags_t = flags::bitfield_flag<std::uint8_t, struct encode_string_flags_tag>;
 
 	namespace string
 	{
diff --git a/include/libtorrent/aux_/session_interface.hpp b/include/libtorrent/aux_/session_interface.hpp
index 7ea4a7903..f39275f48 100644
--- a/include/libtorrent/aux_/session_interface.hpp
+++ b/include/libtorrent/aux_/session_interface.hpp
@@ -89,8 +89,7 @@ namespace libtorrent {
 	struct resolver_interface;
 
 	// hidden
-	struct queue_position_tag;
-	using queue_position_t = aux::strong_typedef<int, queue_position_tag>;
+	using queue_position_t = aux::strong_typedef<int, struct queue_position_tag>;
 
 	constexpr queue_position_t no_pos{-1};
 	constexpr queue_position_t last_pos{(std::numeric_limits<int>::max)()};
@@ -110,8 +109,7 @@ namespace aux {
 	struct session_settings;
 	struct socket_type;
 
-	struct ip_source_tag;
-	using ip_source_t = flags::bitfield_flag<std::uint8_t, ip_source_tag>;
+	using ip_source_t = flags::bitfield_flag<std::uint8_t, struct ip_source_tag>;
 
 #if !defined TORRENT_DISABLE_LOGGING || TORRENT_USE_ASSERTS
 	// This is the basic logging and debug interface offered by the session.
diff --git a/include/libtorrent/create_torrent.hpp b/include/libtorrent/create_torrent.hpp
index 0b1f779e5..ed53b3462 100644
--- a/include/libtorrent/create_torrent.hpp
+++ b/include/libtorrent/create_torrent.hpp
@@ -93,8 +93,7 @@ namespace libtorrent {
 	class torrent_info;
 
 	// hidden
-	struct create_flags_tag;
-	using create_flags_t = flags::bitfield_flag<std::uint32_t, create_flags_tag>;
+	using create_flags_t = flags::bitfield_flag<std::uint32_t, struct create_flags_tag>;
 
 	// This class holds state for creating a torrent. After having added
 	// all information to it, call create_torrent::generate() to generate
diff --git a/include/libtorrent/disk_interface.hpp b/include/libtorrent/disk_interface.hpp
index 559ce4a45..987f6d031 100644
--- a/include/libtorrent/disk_interface.hpp
+++ b/include/libtorrent/disk_interface.hpp
@@ -64,8 +64,7 @@ namespace libtorrent {
 
 	struct storage_holder;
 
-	struct file_open_mode_tag;
-	using file_open_mode_t = flags::bitfield_flag<std::uint8_t, file_open_mode_tag>;
+	using file_open_mode_t = flags::bitfield_flag<std::uint8_t, struct file_open_mode_tag>;
 
 	// this is a bittorrent constant
 	constexpr int default_block_size = 0x4000;
@@ -128,8 +127,7 @@ namespace libtorrent {
 	using pool_file_status = open_file_state;
 #endif
 
-	struct disk_job_flags_tag;
-	using disk_job_flags_t = flags::bitfield_flag<std::uint8_t, disk_job_flags_tag>;
+	using disk_job_flags_t = flags::bitfield_flag<std::uint8_t, struct disk_job_flags_tag>;
 
 	struct TORRENT_EXTRA_EXPORT disk_interface
 	{
diff --git a/include/libtorrent/download_priority.hpp b/include/libtorrent/download_priority.hpp
index 4325e8d2d..fb2108ac4 100644
--- a/include/libtorrent/download_priority.hpp
+++ b/include/libtorrent/download_priority.hpp
@@ -37,8 +37,7 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace libtorrent {
 
-struct download_priority_tag;
-using download_priority_t = aux::strong_typedef<std::uint8_t, download_priority_tag>;
+using download_priority_t = aux::strong_typedef<std::uint8_t, struct download_priority_tag>;
 
 constexpr download_priority_t dont_download{0};
 constexpr download_priority_t default_priority{4};
diff --git a/include/libtorrent/extensions.hpp b/include/libtorrent/extensions.hpp
index c6df595cc..d39d110f7 100644
--- a/include/libtorrent/extensions.hpp
+++ b/include/libtorrent/extensions.hpp
@@ -186,11 +186,9 @@ namespace libtorrent {
 	struct session_handle;
 	struct peer_connection_handle;
 
-	struct feature_flags_tag;
-
 	// these are flags that can be returned by implemented_features()
 	// indicating which callbacks this plugin is interested in
-	using feature_flags_t = flags::bitfield_flag<std::uint8_t, feature_flags_tag>;
+	using feature_flags_t = flags::bitfield_flag<std::uint8_t, struct feature_flags_tag>;
 
 	// this is the base class for a session plugin. One primary feature
 	// is that it is notified of all torrents that are added to the session,
@@ -279,8 +277,7 @@ namespace libtorrent {
 		virtual void load_state(bdecode_node const&) {}
 	};
 
-	struct add_peer_flags_tag;
-	using add_peer_flags_t = flags::bitfield_flag<std::uint8_t, add_peer_flags_tag>;
+	using add_peer_flags_t = flags::bitfield_flag<std::uint8_t, struct add_peer_flags_tag>;
 
 	// Torrent plugins are associated with a single torrent and have a number
 	// of functions called at certain events. Many of its functions have the
diff --git a/include/libtorrent/file.hpp b/include/libtorrent/file.hpp
index 31093e53d..d741399b2 100644
--- a/include/libtorrent/file.hpp
+++ b/include/libtorrent/file.hpp
@@ -128,8 +128,7 @@ namespace libtorrent {
 	using file_handle = std::shared_ptr<file>;
 
 	// hidden
-	struct open_mode_tag;
-	using open_mode_t = flags::bitfield_flag<std::uint32_t, open_mode_tag>;
+	using open_mode_t = flags::bitfield_flag<std::uint32_t, struct open_mode_tag>;
 
 	// the open mode for files. Used for the file constructor or
 	// file::open().
diff --git a/include/libtorrent/file_storage.hpp b/include/libtorrent/file_storage.hpp
index cc10f2373..34f20126a 100644
--- a/include/libtorrent/file_storage.hpp
+++ b/include/libtorrent/file_storage.hpp
@@ -193,8 +193,7 @@ namespace libtorrent {
 	};
 
 	// hidden
-	struct file_flags_tag;
-	using file_flags_t = flags::bitfield_flag<std::uint8_t, file_flags_tag>;
+	using file_flags_t = flags::bitfield_flag<std::uint8_t, struct file_flags_tag>;
 
 	// The ``file_storage`` class represents a file list and the piece
 	// size. Everything necessary to interpret a regular bittorrent storage
diff --git a/include/libtorrent/kademlia/observer.hpp b/include/libtorrent/kademlia/observer.hpp
index 6dcdc5fe5..6d0d31f48 100644
--- a/include/libtorrent/kademlia/observer.hpp
+++ b/include/libtorrent/kademlia/observer.hpp
@@ -48,8 +48,7 @@ struct observer;
 struct msg;
 struct traversal_algorithm;
 
-struct observer_flags_tag;
-using observer_flags_t = libtorrent::flags::bitfield_flag<std::uint8_t, observer_flags_tag>;
+using observer_flags_t = libtorrent::flags::bitfield_flag<std::uint8_t, struct observer_flags_tag>;
 
 struct TORRENT_EXTRA_EXPORT observer
 	: std::enable_shared_from_this<observer>
diff --git a/include/libtorrent/kademlia/traversal_algorithm.hpp b/include/libtorrent/kademlia/traversal_algorithm.hpp
index d45193890..5ec98ef04 100644
--- a/include/libtorrent/kademlia/traversal_algorithm.hpp
+++ b/include/libtorrent/kademlia/traversal_algorithm.hpp
@@ -53,8 +53,7 @@ namespace dht {
 class node;
 struct node_endpoint;
 
-struct traversal_flags_tag;
-using traversal_flags_t = libtorrent::flags::bitfield_flag<std::uint8_t, traversal_flags_tag>;
+using traversal_flags_t = libtorrent::flags::bitfield_flag<std::uint8_t, struct traversal_flags_tag>;
 
 // this class may not be instantiated as a stack object
 struct TORRENT_EXTRA_EXPORT traversal_algorithm
diff --git a/include/libtorrent/link.hpp b/include/libtorrent/link.hpp
index 7520c4046..4d91a9c13 100644
--- a/include/libtorrent/link.hpp
+++ b/include/libtorrent/link.hpp
@@ -38,8 +38,7 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace libtorrent {
 
-	struct torrent_list_tag;
-	using torrent_list_index_t = aux::strong_typedef<int, torrent_list_tag>;
+	using torrent_list_index_t = aux::strong_typedef<int, struct torrent_list_tag>;
 
 	struct link
 	{
diff --git a/include/libtorrent/part_file.hpp b/include/libtorrent/part_file.hpp
index 3353f724d..ab6d6ac47 100644
--- a/include/libtorrent/part_file.hpp
+++ b/include/libtorrent/part_file.hpp
@@ -46,8 +46,7 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace libtorrent {
 
-	struct slot_index_tag_t {};
-	using slot_index_t = aux::strong_typedef<int, slot_index_tag_t>;
+	using slot_index_t = aux::strong_typedef<int, struct slot_index_tag_t>;
 
 	struct TORRENT_EXTRA_EXPORT part_file
 	{
diff --git a/include/libtorrent/peer_class.hpp b/include/libtorrent/peer_class.hpp
index 21aec777c..fe70baf1d 100644
--- a/include/libtorrent/peer_class.hpp
+++ b/include/libtorrent/peer_class.hpp
@@ -46,12 +46,7 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace libtorrent {
 
-	namespace aux {
-
-		struct peer_class_tag;
-	}
-
-	using peer_class_t = aux::strong_typedef<std::uint32_t, aux::peer_class_tag>;
+	using peer_class_t = aux::strong_typedef<std::uint32_t, struct peer_class_tag>;
 
 	// holds settings for a peer class. Used in set_peer_class() and
 	// get_peer_class() calls.
diff --git a/include/libtorrent/peer_connection.hpp b/include/libtorrent/peer_connection.hpp
index a4d482ff1..8b9bdb994 100644
--- a/include/libtorrent/peer_connection.hpp
+++ b/include/libtorrent/peer_connection.hpp
@@ -242,8 +242,7 @@ namespace aux {
 		http_seed
 	};
 
-	struct request_flags_tag;
-	using request_flags_t = flags::bitfield_flag<std::uint8_t, request_flags_tag>;
+	using request_flags_t = flags::bitfield_flag<std::uint8_t, struct request_flags_tag>;
 
 	class TORRENT_EXTRA_EXPORT peer_connection
 		: public peer_connection_hot_members
diff --git a/include/libtorrent/peer_info.hpp b/include/libtorrent/peer_info.hpp
index 5535064d7..8dffe57fc 100644
--- a/include/libtorrent/peer_info.hpp
+++ b/include/libtorrent/peer_info.hpp
@@ -44,24 +44,19 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace libtorrent {
 
-	// hidden
-	struct peer_flags_tag;
-	struct peer_source_flags_tag;
-	struct bandwidth_state_flags_tag;
-
 	// flags for the peer_info::flags field. Indicates various states
 	// the peer may be in. These flags are not mutually exclusive, but
 	// not every combination of them makes sense either.
-	using peer_flags_t = flags::bitfield_flag<std::uint32_t, peer_flags_tag>;
+	using peer_flags_t = flags::bitfield_flag<std::uint32_t, struct peer_flags_tag>;
 
 	// the flags indicating which sources a peer can
 	// have come from. A peer may have been seen from
 	// multiple sources
-	using peer_source_flags_t = flags::bitfield_flag<std::uint8_t, peer_source_flags_tag>;
+	using peer_source_flags_t = flags::bitfield_flag<std::uint8_t, struct peer_source_flags_tag>;
 
 	// flags indicating what is blocking network transfers in up- and down
 	// direction
-	using bandwidth_state_flags_t = flags::bitfield_flag<std::uint8_t, bandwidth_state_flags_tag>;
+	using bandwidth_state_flags_t = flags::bitfield_flag<std::uint8_t, struct bandwidth_state_flags_tag>;
 
 	// holds information and statistics about one peer
 	// that libtorrent is connected to
diff --git a/include/libtorrent/pex_flags.hpp b/include/libtorrent/pex_flags.hpp
index 6f96c3f16..03bf4436a 100644
--- a/include/libtorrent/pex_flags.hpp
+++ b/include/libtorrent/pex_flags.hpp
@@ -37,8 +37,7 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace libtorrent {
 
-	struct pex_flags_tag;
-	using pex_flags_t = flags::bitfield_flag<std::uint8_t, pex_flags_tag>;
+	using pex_flags_t = flags::bitfield_flag<std::uint8_t, struct pex_flags_tag>;
 
 	// these flags match the flags passed in ut_pex
 	// messages
diff --git a/include/libtorrent/piece_picker.hpp b/include/libtorrent/piece_picker.hpp
index ab21d7872..e58edd436 100644
--- a/include/libtorrent/piece_picker.hpp
+++ b/include/libtorrent/piece_picker.hpp
@@ -63,11 +63,8 @@ namespace libtorrent {
 	struct counters;
 	struct torrent_peer;
 
-	struct prio_index_tag_t {};
-	using prio_index_t = aux::strong_typedef<int, prio_index_tag_t>;
-
-	struct picker_options_tag;
-	using picker_options_t = flags::bitfield_flag<std::uint16_t, picker_options_tag>;
+	using prio_index_t = aux::strong_typedef<int, struct prio_index_tag_t>;
+	using picker_options_t = flags::bitfield_flag<std::uint16_t, struct picker_options_tag>;
 
 	class TORRENT_EXTRA_EXPORT piece_picker
 	{
diff --git a/include/libtorrent/portmap.hpp b/include/libtorrent/portmap.hpp
index 3462fa177..3a995cfb3 100644
--- a/include/libtorrent/portmap.hpp
+++ b/include/libtorrent/portmap.hpp
@@ -37,9 +37,6 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/units.hpp"
 
 namespace libtorrent {
-namespace aux {
-	struct port_mapping_tag;
-}
 
 	enum class portmap_transport : std::uint8_t
 	{
@@ -52,7 +49,7 @@ namespace aux {
 	};
 
 	// this type represents an index referring to a port mapping
-	using port_mapping_t = aux::strong_typedef<int, aux::port_mapping_tag>;
+	using port_mapping_t = aux::strong_typedef<int, struct port_mapping_tag>;
 
 }
 
diff --git a/include/libtorrent/resolver_interface.hpp b/include/libtorrent/resolver_interface.hpp
index e7936a0c0..509bcdd0b 100644
--- a/include/libtorrent/resolver_interface.hpp
+++ b/include/libtorrent/resolver_interface.hpp
@@ -44,8 +44,7 @@ POSSIBILITY OF SUCH DAMAGE.
 namespace libtorrent {
 
 // hidden
-struct resolver_flag_tag;
-using resolver_flags = flags::bitfield_flag<std::uint8_t, resolver_flag_tag>;
+using resolver_flags = flags::bitfield_flag<std::uint8_t, struct resolver_flag_tag>;
 
 struct TORRENT_EXTRA_EXPORT resolver_interface
 {
diff --git a/include/libtorrent/session_types.hpp b/include/libtorrent/session_types.hpp
index 15b1b7227..1a5a3b09b 100644
--- a/include/libtorrent/session_types.hpp
+++ b/include/libtorrent/session_types.hpp
@@ -39,20 +39,16 @@ POSSIBILITY OF SUCH DAMAGE.
 namespace libtorrent {
 
 	// hidden
-	struct save_state_flags_tag;
-	using save_state_flags_t = flags::bitfield_flag<std::uint32_t, save_state_flags_tag>;
+	using save_state_flags_t = flags::bitfield_flag<std::uint32_t, struct save_state_flags_tag>;
 
 	// hidden
-	struct session_flags_tag;
-	using session_flags_t = flags::bitfield_flag<std::uint8_t, session_flags_tag>;
+	using session_flags_t = flags::bitfield_flag<std::uint8_t, struct session_flags_tag>;
 
 	// hidden
-	struct remove_flags_tag;
-	using remove_flags_t = flags::bitfield_flag<std::uint8_t, remove_flags_tag>;
+	using remove_flags_t = flags::bitfield_flag<std::uint8_t, struct remove_flags_tag>;
 
 	// hidden
-	struct reopen_network_flags_tag;
-	using reopen_network_flags_t = flags::bitfield_flag<std::uint8_t, reopen_network_flags_tag>;
+	using reopen_network_flags_t = flags::bitfield_flag<std::uint8_t, struct reopen_network_flags_tag>;
 }
 
 #endif
diff --git a/include/libtorrent/storage_defs.hpp b/include/libtorrent/storage_defs.hpp
index 9a79f3fd4..f06c1c595 100644
--- a/include/libtorrent/storage_defs.hpp
+++ b/include/libtorrent/storage_defs.hpp
@@ -48,8 +48,7 @@ namespace libtorrent {
 	struct file_pool;
 	class torrent_info;
 
-	struct storage_index_tag_t {};
-	using storage_index_t = aux::strong_typedef<std::uint32_t, storage_index_tag_t>;
+	using storage_index_t = aux::strong_typedef<std::uint32_t, struct storage_index_tag_t>;
 
 	// types of storage allocation used for add_torrent_params::storage_mode.
 	enum storage_mode_t
diff --git a/include/libtorrent/torrent_flags.hpp b/include/libtorrent/torrent_flags.hpp
index 3d3a105f2..a2a4f2459 100644
--- a/include/libtorrent/torrent_flags.hpp
+++ b/include/libtorrent/torrent_flags.hpp
@@ -37,8 +37,7 @@ POSSIBILITY OF SUCH DAMAGE.
 
 namespace libtorrent {
 
-struct torrent_flags_tag;
-using torrent_flags_t = flags::bitfield_flag<std::uint64_t, torrent_flags_tag>;
+using torrent_flags_t = flags::bitfield_flag<std::uint64_t, struct torrent_flags_tag>;
 
 namespace torrent_flags {
 
diff --git a/include/libtorrent/torrent_handle.hpp b/include/libtorrent/torrent_handle.hpp
index ec96fbfd9..3daead524 100644
--- a/include/libtorrent/torrent_handle.hpp
+++ b/include/libtorrent/torrent_handle.hpp
@@ -80,33 +80,16 @@ namespace aux {
 	struct storage_interface;
 	class torrent;
 
-	// hidden
-	struct status_flags_tag;
-	using status_flags_t = flags::bitfield_flag<std::uint32_t, status_flags_tag>;
-
 #ifndef BOOST_NO_EXCEPTIONS
 	void TORRENT_NO_RETURN throw_invalid_handle();
 #endif
 
-	// hidden
-	struct add_piece_flags_tag;
-	using add_piece_flags_t = flags::bitfield_flag<std::uint8_t, add_piece_flags_tag>;
-
-	// hidden
-	struct pause_flags_tag;
-	using pause_flags_t = flags::bitfield_flag<std::uint8_t, pause_flags_tag>;
-
-	// hidden
-	struct deadline_flags_tag;
-	using deadline_flags_t = flags::bitfield_flag<std::uint8_t, deadline_flags_tag>;
-
-	// hidden
-	struct resume_data_flags_tag;
-	using resume_data_flags_t = flags::bitfield_flag<std::uint8_t, resume_data_flags_tag>;
-
-	// hidden
-	struct queue_position_tag;
-	using queue_position_t = aux::strong_typedef<int, queue_position_tag>;
+	using status_flags_t = flags::bitfield_flag<std::uint32_t, struct status_flags_tag>;
+	using add_piece_flags_t = flags::bitfield_flag<std::uint8_t, struct add_piece_flags_tag>;
+	using pause_flags_t = flags::bitfield_flag<std::uint8_t, struct pause_flags_tag>;
+	using deadline_flags_t = flags::bitfield_flag<std::uint8_t, struct deadline_flags_tag>;
+	using resume_data_flags_t = flags::bitfield_flag<std::uint8_t, struct resume_data_flags_tag>;
+	using queue_position_t = aux::strong_typedef<int, struct queue_position_tag>;
 
 	// holds the state of a block in a piece. Who we requested
 	// it from and how far along we are at downloading it.
diff --git a/include/libtorrent/udp_socket.hpp b/include/libtorrent/udp_socket.hpp
index 3a5e33874..b684ca435 100644
--- a/include/libtorrent/udp_socket.hpp
+++ b/include/libtorrent/udp_socket.hpp
@@ -48,8 +48,7 @@ namespace libtorrent {
 
 	struct socks5;
 
-	struct udp_send_flags_tag;
-	using udp_send_flags_t = flags::bitfield_flag<std::uint8_t, udp_send_flags_tag>;
+	using udp_send_flags_t = flags::bitfield_flag<std::uint8_t, struct udp_send_flags_tag>;
 
 	class TORRENT_EXTRA_EXPORT udp_socket : single_threaded
 	{
diff --git a/test/swarm_suite.hpp b/test/swarm_suite.hpp
index 8aa520c3a..9668c9e28 100644
--- a/test/swarm_suite.hpp
+++ b/test/swarm_suite.hpp
@@ -33,16 +33,16 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "test.hpp"
 #include "libtorrent/flags.hpp"
 
-struct test_flags_tag;
-using test_flags_t = libtorrent::flags::bitfield_flag<std::uint32_t, test_flags_tag>;
+using test_flags_t = libtorrent::flags::bitfield_flag<std::uint32_t, struct test_flags_tag>;
 
 namespace test_flags
 {
-	constexpr test_flags_t super_seeding{1};
-	constexpr test_flags_t strict_super_seeding{2};
-	constexpr test_flags_t seed_mode{4};
-	constexpr test_flags_t time_critical{8};
-	constexpr test_flags_t suggest{16};
+	using libtorrent::operator ""_bit;
+	constexpr test_flags_t super_seeding = 1_bit;
+	constexpr test_flags_t strict_super_seeding = 2_bit;
+	constexpr test_flags_t seed_mode = 3_bit;
+	constexpr test_flags_t time_critical = 4_bit;
+	constexpr test_flags_t suggest = 5_bit;
 }
 
 EXPORT void test_swarm(test_flags_t flags = test_flags_t{});
diff --git a/test/test_resume.cpp b/test/test_resume.cpp
index 6769027f1..2cc0837aa 100644
--- a/test/test_resume.cpp
+++ b/test/test_resume.cpp
@@ -938,8 +938,7 @@ TORRENT_TEST(zero_file_prio)
 	test_zero_file_prio();
 }
 
-struct test_mode_tag;
-using test_mode_t = flags::bitfield_flag<std::uint8_t, test_mode_tag>;
+using test_mode_t = flags::bitfield_flag<std::uint8_t, struct test_mode_tag>;
 
 namespace test_mode {
 	constexpr test_mode_t file_prio = 0_bit;
diff --git a/test/test_transfer.cpp b/test/test_transfer.cpp
index ffb803235..f39a2624e 100644
--- a/test/test_transfer.cpp
+++ b/test/test_transfer.cpp
@@ -122,8 +122,7 @@ storage_interface* test_storage_constructor(storage_params const& params, file_p
 	return new test_storage(params, pool);
 }
 
-struct transfer_tag;
-using transfer_flags_t = lt::flags::bitfield_flag<std::uint8_t, transfer_tag>;
+using transfer_flags_t = lt::flags::bitfield_flag<std::uint8_t, struct transfer_tag>;
 
 constexpr transfer_flags_t disk_full = 1_bit;
 constexpr transfer_flags_t delete_files = 2_bit;