diff --git a/src/music/win32_m.cpp b/src/music/win32_m.cpp
--- a/src/music/win32_m.cpp
+++ b/src/music/win32_m.cpp
@@ -42,7 +42,7 @@ static struct {
 
 	MidiFile current_file;           ///< file currently being played from
 	PlaybackSegment current_segment; ///< segment info for current playback
-	DWORD playback_start_time;       ///< timestamp current file began playback
+	size_t playback_start_time;      ///< timestamp current file began playback
 	size_t current_block;            ///< next block index to send
 	MidiFile next_file;              ///< upcoming file to play
 	PlaybackSegment next_segment;    ///< segment info for upcoming file
@@ -184,7 +184,7 @@ void CALLBACK TimerCallback(UINT uTimerI
 		/* find first block after start time and pretend playback started earlier
 		* this is to allow all blocks prior to the actual start to still affect playback,
 		* as they may contain important controller and program changes */
-		uint preload_bytes = 0;
+		size_t preload_bytes = 0;
 		for (size_t bl = 0; bl < _midi.current_file.blocks.size(); bl++) {
 			MidiFile::DataBlock &block = _midi.current_file.blocks[bl];
 			preload_bytes += block.data.size();
@@ -210,7 +210,7 @@ void CALLBACK TimerCallback(UINT uTimerI
 
 	/* play pending blocks */
 	DWORD current_time = timeGetTime();
-	DWORD playback_time = current_time - _midi.playback_start_time;
+	size_t playback_time = current_time - _midi.playback_start_time;
 	while (_midi.current_block < _midi.current_file.blocks.size()) {
 		MidiFile::DataBlock &block = _midi.current_file.blocks[_midi.current_block];