diff --git a/plugins/obs-ffmpeg/ffmpeg-mux/ffmpeg-mux.c b/plugins/obs-ffmpeg/ffmpeg-mux/ffmpeg-mux.c
index abb3913d4..2b97754bd 100644
--- a/plugins/obs-ffmpeg/ffmpeg-mux/ffmpeg-mux.c
+++ b/plugins/obs-ffmpeg/ffmpeg-mux/ffmpeg-mux.c
@@ -780,7 +780,12 @@ static void *ffmpeg_mux_io_thread(void *data)
 			if (want_seek) {
 				os_fseeki64(ffm->io.output_file,
 					    next_seek_position, SEEK_SET);
-				current_seek_position = next_seek_position;
+
+				// Update the next virtual position, making sure to take
+				// into account the size of the chunk we're about to write.
+				current_seek_position =
+					next_seek_position + chunk_used;
+
 				want_seek = false;
 			}