diff --git a/plugins/obs-ffmpeg/ffmpeg-mux/ffmpeg-mux.c b/plugins/obs-ffmpeg/ffmpeg-mux/ffmpeg-mux.c
index 30fcc8b3a..f15342128 100644
--- a/plugins/obs-ffmpeg/ffmpeg-mux/ffmpeg-mux.c
+++ b/plugins/obs-ffmpeg/ffmpeg-mux/ffmpeg-mux.c
@@ -124,7 +124,7 @@ struct audio_info {
 
 struct io_header {
 	uint64_t seek_offset;
-	uint64_t data_length;
+	size_t data_length;
 };
 
 struct io_buffer {